Move all the Active Record validations to Active Model

22 files changed, 555 insertions, 1353 deletions

diff --git a/activemodel/lib/active_model.rb b/activemodel/lib/active_model.rb
index 4ed7b0889d..e777351cea 100644
--- a/activemodel/lib/active_model.rb
+++ b/activemodel/lib/active_model.rb
@@ -1,5 +1,43 @@
-require 'active_model/observing'
-# disabled until they're tested
-# require 'active_model/callbacks'
-# require 'active_model/validations'
-require 'active_model/base'
\ No newline at end of file
+#--
+# Copyright (c) 2004-2009 David Heinemeier Hansson
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+#++
+
+begin
+  require 'active_support'
+rescue LoadError
+  activesupport_path = "#{File.dirname(__FILE__)}/../../activesupport/lib"
+  if File.directory?(activesupport_path)
+    $:.unshift activesupport_path
+    require 'active_support'
+  end
+end
+
+module ActiveModel
+  def self.load_all!
+    [Base]
+  end
+
+  autoload :Base, 'active_model/base'
+  autoload :Validations, 'active_model/validations'
+  autoload :Errors, 'active_model/errors'
+  autoload :DeprecatedErrorMethods, 'active_model/deprecated_error_methods'
+end
diff --git a/activemodel/lib/active_model/deprecated_error_methods.rb b/activemodel/lib/active_model/deprecated_error_methods.rb
index e0cbd9ba29..b0d7023046 100644
--- a/activemodel/lib/active_model/deprecated_error_methods.rb
+++ b/activemodel/lib/active_model/deprecated_error_methods.rb
@@ -1,37 +1,28 @@
 module ActiveModel
   module DeprecatedErrorMethods
     def on(attribute)
-      ActiveSupport::Deprecation.warn "Errors#on have been deprecated, use Errors#[] instead"
-      self[attribute]
+      # ActiveSupport::Deprecation.warn "Errors#on have been deprecated, use Errors#[] instead"
+      errors = self[attribute]
+      errors.size < 2 ? errors.first : errors
     end
 
     def on_base
-      ActiveSupport::Deprecation.warn "Errors#on_base have been deprecated, use Errors#[:base] instead"
+      # ActiveSupport::Deprecation.warn "Errors#on_base have been deprecated, use Errors#[:base] instead"
       on(:base)
     end
 
-    def add(attribute, msg = Errors.default_error_messages[:invalid])
-      ActiveSupport::Deprecation.warn "Errors#add(attribute, msg) has been deprecated, use Errors#[attribute] << msg instead"
-      self[attribute] << msg
-    end
-
     def add_to_base(msg)
-      ActiveSupport::Deprecation.warn "Errors#add_to_base(msg) has been deprecated, use Errors#[:base] << msg instead"
+      # ActiveSupport::Deprecation.warn "Errors#add_to_base(msg) has been deprecated, use Errors#[:base] << msg instead"
       self[:base] << msg
     end
   
     def invalid?(attribute)
-      ActiveSupport::Deprecation.warn "Errors#invalid?(attribute) has been deprecated, use Errors#[attribute].any? instead"
+      # ActiveSupport::Deprecation.warn "Errors#invalid?(attribute) has been deprecated, use Errors#[attribute].any? instead"
       self[attribute].any?
     end
 
-    def full_messages
-      ActiveSupport::Deprecation.warn "Errors#full_messages has been deprecated, use Errors#to_a instead"
-      to_a
-    end
-
     def each_full
-      ActiveSupport::Deprecation.warn "Errors#each_full has been deprecated, use Errors#to_a.each instead"
+      # ActiveSupport::Deprecation.warn "Errors#each_full has been deprecated, use Errors#to_a.each instead"
       to_a.each { |error| yield error }
     end
   end
diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index bcf0810290..ad7ed723a1 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -1,40 +1,27 @@
 module ActiveModel
   class Errors < Hash
     include DeprecatedErrorMethods
-    
-    @@default_error_messages = {
-      :inclusion                => "is not included in the list",
-      :exclusion                => "is reserved",
-      :invalid                  => "is invalid",
-      :confirmation             => "doesn't match confirmation",
-      :accepted                 => "must be accepted",
-      :empty                    => "can't be empty",
-      :blank                    => "can't be blank",
-      :too_long                 => "is too long (maximum is %d characters)",
-      :too_short                => "is too short (minimum is %d characters)",
-      :wrong_length             => "is the wrong length (should be %d characters)",
-      :taken                    => "has already been taken",
-      :not_a_number             => "is not a number",
-      :greater_than             => "must be greater than %d",
-      :greater_than_or_equal_to => "must be greater than or equal to %d",
-      :equal_to                 => "must be equal to %d",
-      :less_than                => "must be less than %d",
-      :less_than_or_equal_to    => "must be less than or equal to %d",
-      :odd                      => "must be odd",
-      :even                     => "must be even"
-    }
-  
-    ##
-    # :singleton-method:
-    # Holds a hash with all the default error messages that can be replaced by your own copy or localizations.
-    cattr_accessor :default_error_messages
+
+    class << self
+      def default_error_messages
+        message = "Errors.default_error_messages has been deprecated. Please use I18n.translate('activerecord.errors.messages')."
+        ActiveSupport::Deprecation.warn(message)
+
+        I18n.translate 'activerecord.errors.messages'
+      end
+    end
+
+    def initialize(base)
+      @base = base
+      super()
+    end
 
     alias_method :get, :[]
     alias_method :set, :[]=
 
     def [](attribute)
       if errors = get(attribute.to_sym)
-        errors.size == 1 ? errors.first : errors
+        errors
       else
         set(attribute.to_sym, [])
       end
@@ -55,17 +42,11 @@ module ActiveModel
     end
 
     def to_a
-      inject([]) do |errors_with_attributes, (attribute, errors)|
-        if error.blank?
-          errors_with_attributes
-        else
-          if attr == :base
-            errors_with_attributes << error
-          else
-            errors_with_attributes << (attribute.to_s.humanize + " " + error)
-          end
-        end
-      end
+      full_messages
+    end
+
+    def count
+      to_a.size
     end
 
     def to_xml(options={})
@@ -78,5 +59,106 @@ module ActiveModel
         to_a.each { |error| e.error(error) }
       end
     end
+
+    # Adds an error message (+messsage+) to the +attribute+, which will be returned on a call to <tt>on(attribute)</tt>
+    # for the same attribute and ensure that this error object returns false when asked if <tt>empty?</tt>. More than one
+    # error can be added to the same +attribute+ in which case an array will be returned on a call to <tt>on(attribute)</tt>.
+    # If no +messsage+ is supplied, :invalid is assumed.
+    # If +message+ is a Symbol, it will be translated, using the appropriate scope (see translate_error).
+    def add(attribute, message = nil, options = {})
+      message ||= :invalid
+      message = generate_message(attribute, message, options) if message.is_a?(Symbol)
+      self[attribute] << message
+    end
+
+    # Will add an error message to each of the attributes in +attributes+ that is empty.
+    def add_on_empty(attributes, custom_message = nil)
+      [attributes].flatten.each do |attribute|
+        value = @base.respond_to?(attribute.to_s) ? @base.send(attribute.to_s) : @base[attribute.to_s]
+        is_empty = value.respond_to?(:empty?) ? value.empty? : false
+        add(attribute, :empty, :default => custom_message) unless !value.nil? && !is_empty
+      end
+    end
+
+    # Will add an error message to each of the attributes in +attributes+ that is blank (using Object#blank?).
+    def add_on_blank(attributes, custom_message = nil)
+      [attributes].flatten.each do |attribute|
+        value = @base.respond_to?(attribute.to_sym) ? @base.send(attribute.to_sym) : @base[attribute.to_sym]
+        add(attribute, :blank, :default => custom_message) if value.blank?
+      end
+    end
+
+    # Returns all the full error messages in an array.
+    #
+    #   class Company < ActiveRecord::Base
+    #     validates_presence_of :name, :address, :email
+    #     validates_length_of :name, :in => 5..30
+    #   end
+    #
+    #   company = Company.create(:address => '123 First St.')
+    #   company.errors.full_messages # =>
+    #     ["Name is too short (minimum is 5 characters)", "Name can't be blank", "Address can't be blank"]
+    def full_messages(options = {})
+      full_messages = []
+
+      each do |attribute, messages|
+        next if messages.empty?
+
+        if attribute == :base
+          messages.each {|m| full_messages << m }
+        else
+          attr_name = @base.class.human_attribute_name(attribute.to_s)
+          prefix = attr_name + I18n.t('activerecord.errors.format.separator', :default => ' ')
+          messages.each do |m|
+            full_messages <<  "#{prefix}#{m}"
+          end
+        end
+      end
+
+      full_messages
+    end
+
+    # Translates an error message in it's default scope (<tt>activerecord.errrors.messages</tt>).
+    # Error messages are first looked up in <tt>models.MODEL.attributes.ATTRIBUTE.MESSAGE</tt>, if it's not there, 
+    # it's looked up in <tt>models.MODEL.MESSAGE</tt> and if that is not there it returns the translation of the 
+    # default message (e.g. <tt>activerecord.errors.messages.MESSAGE</tt>). The translated model name, 
+    # translated attribute name and the value are available for interpolation.
+    #
+    # When using inheritence in your models, it will check all the inherited models too, but only if the model itself
+    # hasn't been found. Say you have <tt>class Admin < User; end</tt> and you wanted the translation for the <tt>:blank</tt>
+    # error +message+ for the <tt>title</tt> +attribute+, it looks for these translations:
+    # 
+    # <ol>
+    # <li><tt>activerecord.errors.models.admin.attributes.title.blank</tt></li>
+    # <li><tt>activerecord.errors.models.admin.blank</tt></li>
+    # <li><tt>activerecord.errors.models.user.attributes.title.blank</tt></li>
+    # <li><tt>activerecord.errors.models.user.blank</tt></li>
+    # <li><tt>activerecord.errors.messages.blank</tt></li>
+    # <li>any default you provided through the +options+ hash (in the activerecord.errors scope)</li>
+    # </ol>
+    def generate_message(attribute, message = :invalid, options = {})
+      message, options[:default] = options[:default], message if options[:default].is_a?(Symbol)
+
+      defaults = @base.class.self_and_descendants_from_active_record.map do |klass|
+        [ :"models.#{klass.name.underscore}.attributes.#{attribute}.#{message}", 
+          :"models.#{klass.name.underscore}.#{message}" ]
+      end
+      
+      defaults << options.delete(:default)
+      defaults = defaults.compact.flatten << :"messages.#{message}"
+
+      key = defaults.shift
+      value = @base.respond_to?(attribute) ? @base.send(attribute) : nil
+
+      options = { :default => defaults,
+        :model => @base.class.human_name,
+        :attribute => @base.class.human_attribute_name(attribute.to_s),
+        :value => value,
+        :scope => [:activerecord, :errors]
+      }.merge(options)
+
+      I18n.translate(key, options)
+    end
+
   end
 end
\ No newline at end of file
diff --git a/activemodel/lib/active_model/validations.rb b/activemodel/lib/active_model/validations.rb
index 460d2d82e5..3ea17381c9 100644
--- a/activemodel/lib/active_model/validations.rb
+++ b/activemodel/lib/active_model/validations.rb
@@ -38,7 +38,7 @@ module ActiveModel
       #   end
       #
       # This usage applies to +validate_on_create+ and +validate_on_update as well+.
-      #
+
       # Validates each attribute against a block.
       #
       #   class Person < ActiveRecord::Base
@@ -48,7 +48,7 @@ module ActiveModel
       #   end
       #
       # Options:
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>)
+      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
       # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+.
       # * <tt>:allow_blank</tt> - Skip validation if attribute is blank.
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
@@ -83,7 +83,7 @@ module ActiveModel
 
     # Returns the Errors object that holds all information about attribute error messages.
     def errors
-      @errors ||= Errors.new
+      @errors ||= Errors.new(self)
     end
 
     # Runs all the specified validations and returns true if no errors were added otherwise false.
@@ -92,35 +92,52 @@ module ActiveModel
 
       run_callbacks(:validate)
       
-      if responds_to?(:validate)
-        ActiveSupport::Deprecations.warn "Base#validate has been deprecated, please use Base.validate :method instead"
+      if respond_to?(:validate)
+        # ActiveSupport::Deprecation.warn "Base#validate has been deprecated, please use Base.validate :method instead"
         validate
       end
 
       if new_record?
         run_callbacks(:validate_on_create)
 
-        if responds_to?(:validate_on_create)
-          ActiveSupport::Deprecations.warn(
-            "Base#validate_on_create has been deprecated, please use Base.validate_on_create :method instead")
+        if respond_to?(:validate_on_create)
+          # ActiveSupport::Deprecation.warn "Base#validate_on_create has been deprecated, please use Base.validate_on_create :method instead"
           validate_on_create
         end
       else
         run_callbacks(:validate_on_update)
 
-        if responds_to?(:validate_on_update)
-          ActiveSupport::Deprecations.warn(
-            "Base#validate_on_update has been deprecated, please use Base.validate_on_update :method instead")
+        if respond_to?(:validate_on_update)
+          # ActiveSupport::Deprecation.warn "Base#validate_on_update has been deprecated, please use Base.validate_on_update :method instead"
           validate_on_update
         end
       end
 
       errors.empty?
     end
+
+    # Performs the opposite of <tt>valid?</tt>. Returns true if errors were added, false otherwise.
+    def invalid?
+      !valid?
+    end
+
+    protected
+    
+    # Overwrite this method for validation checks on all saves and use <tt>Errors.add(field, msg)</tt> for invalid attributes.
+    def validate
+    end
+
+    # Overwrite this method for validation checks used only on creation.
+    def validate_on_create
+    end
+
+    # Overwrite this method for validation checks used only on updates.
+    def validate_on_update
+    end
   end
 end
 
 Dir[File.dirname(__FILE__) + "/validations/*.rb"].sort.each do |path|
   filename = File.basename(path)
   require "active_model/validations/#{filename}"
-end
\ No newline at end of file
+end
diff --git a/activemodel/lib/active_model/validations/acceptance.rb b/activemodel/lib/active_model/validations/acceptance.rb
index 9be7d51ffb..db1fd04bb5 100644
--- a/activemodel/lib/active_model/validations/acceptance.rb
+++ b/activemodel/lib/active_model/validations/acceptance.rb
@@ -8,16 +8,16 @@ module ActiveModel
       #     validates_acceptance_of :eula, :message => "must be abided"
       #   end
       #
-      # If the database column does not exist, the <tt>:terms_of_service</tt> attribute is entirely virtual. This check is
-      # performed only if <tt>:terms_of_service</tt> is not +nil+ and by default on save.
+      # If the database column does not exist, the +terms_of_service+ attribute is entirely virtual. This check is
+      # performed only if +terms_of_service+ is not +nil+ and by default on save.
       #
       # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "must be accepted")
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>)
-      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+. (default is +true+)
+      # * <tt>:message</tt> - A custom error message (default is: "must be accepted").
+      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
+      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+ (default is true).
       # * <tt>:accept</tt> - Specifies value that is considered accepted.  The default value is a string "1", which
       #   makes it easy to relate to an HTML checkbox. This should be set to +true+ if you are validating a database
-      #   column, since the attribute is typecasted from "1" to +true+ before validation.
+      #   column, since the attribute is typecast from "1" to +true+ before validation.
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
@@ -25,19 +25,22 @@ module ActiveModel
       #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
       def validates_acceptance_of(*attr_names)
-        configuration = { :message => ActiveRecord::Errors.default_error_messages[:accepted], :on => :save, :allow_nil => true, :accept => "1" }
+        configuration = { :on => :save, :allow_nil => true, :accept => "1" }
         configuration.update(attr_names.extract_options!)
 
         db_cols = begin
           column_names
-        rescue ActiveRecord::StatementInvalid
+        rescue Exception # To ignore both statement and connection errors
           []
         end
+
         names = attr_names.reject { |name| db_cols.include?(name.to_s) }
         attr_accessor(*names)
 
         validates_each(attr_names,configuration) do |record, attr_name, value|
-          record.errors.add(attr_name, configuration[:message]) unless value == configuration[:accept]
+          unless value == configuration[:accept]
+            record.errors.add(attr_name, :accepted, :default => configuration[:message]) 
+          end
         end
       end
     end
diff --git a/activemodel/lib/active_model/validations/associated.rb b/activemodel/lib/active_model/validations/associated.rb
index b2d78af580..ba4af5d66d 100644
--- a/activemodel/lib/active_model/validations/associated.rb
+++ b/activemodel/lib/active_model/validations/associated.rb
@@ -18,14 +18,14 @@ module ActiveModel
       #     validates_associated :book
       #   end
       #
-      # ...this would specify a circular dependency and cause infinite recursion.
+      # this would specify a circular dependency and cause infinite recursion.
       #
       # NOTE: This validation will not fail if the association hasn't been assigned. If you want to ensure that the association
       # is both present and guaranteed to be valid, you also need to use +validates_presence_of+.
       #
       # Configuration options:
       # * <tt>:message</tt> - A custom error message (default is: "is invalid")
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>)
+      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
@@ -33,12 +33,13 @@ module ActiveModel
       #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
       def validates_associated(*attr_names)
-        configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save }
+        configuration = { :on => :save }
         configuration.update(attr_names.extract_options!)
 
         validates_each(attr_names, configuration) do |record, attr_name, value|
-          record.errors.add(attr_name, configuration[:message]) unless
-            (value.is_a?(Array) ? value : [value]).inject(true) { |v, r| (r.nil? || r.valid?) && v }
+          unless (value.is_a?(Array) ? value : [value]).collect { |r| r.nil? || r.valid? }.all?
+            record.errors.add(attr_name, :invalid, :default => configuration[:message], :value => value)
+          end
         end
       end
     end
diff --git a/activemodel/lib/active_model/validations/confirmation.rb b/activemodel/lib/active_model/validations/confirmation.rb
index ba4a18adb7..5f18da58e3 100644
--- a/activemodel/lib/active_model/validations/confirmation.rb
+++ b/activemodel/lib/active_model/validations/confirmation.rb
@@ -21,8 +21,8 @@ module ActiveModel
       #   validates_presence_of :password_confirmation, :if => :password_changed?
       #
       # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "doesn't match confirmation")
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>)
+      # * <tt>:message</tt> - A custom error message (default is: "doesn't match confirmation").
+      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
@@ -30,13 +30,15 @@ module ActiveModel
       #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
       def validates_confirmation_of(*attr_names)
-        configuration = { :message => ActiveRecord::Errors.default_error_messages[:confirmation], :on => :save }
+        configuration = { :on => :save }
         configuration.update(attr_names.extract_options!)
 
         attr_accessor(*(attr_names.map { |n| "#{n}_confirmation" }))
 
         validates_each(attr_names, configuration) do |record, attr_name, value|
-          record.errors.add(attr_name, configuration[:message]) unless record.send("#{attr_name}_confirmation").nil? or value == record.send("#{attr_name}_confirmation")
+          unless record.send("#{attr_name}_confirmation").nil? or value == record.send("#{attr_name}_confirmation")
+            record.errors.add(attr_name, :confirmation, :default => configuration[:message]) 
+          end
         end
       end
     end
diff --git a/activemodel/lib/active_model/validations/exclusion.rb b/activemodel/lib/active_model/validations/exclusion.rb
index 1592000fc7..435ba5cab6 100644
--- a/activemodel/lib/active_model/validations/exclusion.rb
+++ b/activemodel/lib/active_model/validations/exclusion.rb
@@ -6,14 +6,14 @@ module ActiveModel
       #   class Person < ActiveRecord::Base
       #     validates_exclusion_of :username, :in => %w( admin superuser ), :message => "You don't belong here"
       #     validates_exclusion_of :age, :in => 30..60, :message => "This site is only for under 30 and over 60"
-      #     validates_exclusion_of :format, :in => %w( mov avi ), :message => "extension %s is not allowed"
+      #     validates_exclusion_of :format, :in => %w( mov avi ), :message => "extension {{value}} is not allowed"
       #   end
       #
       # Configuration options:
-      # * <tt>:in</tt> - An enumerable object of items that the value shouldn't be part of
-      # * <tt>:message</tt> - Specifies a custom error message (default is: "is reserved")
-      # * <tt>:allow_nil</tt> - If set to +true+, skips this validation if the attribute is +nil+ (default is: +false+)
-      # * <tt>:allow_blank</tt> - If set to +true+, skips this validation if the attribute is blank (default is: +false+)
+      # * <tt>:in</tt> - An enumerable object of items that the value shouldn't be part of.
+      # * <tt>:message</tt> - Specifies a custom error message (default is: "is reserved").
+      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
+      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
@@ -21,7 +21,7 @@ module ActiveModel
       #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
       def validates_exclusion_of(*attr_names)
-        configuration = { :message => ActiveRecord::Errors.default_error_messages[:exclusion], :on => :save }
+        configuration = { :on => :save }
         configuration.update(attr_names.extract_options!)
 
         enum = configuration[:in] || configuration[:within]
@@ -29,7 +29,9 @@ module ActiveModel
         raise(ArgumentError, "An object with the method include? is required must be supplied as the :in option of the configuration hash") unless enum.respond_to?(:include?)
 
         validates_each(attr_names, configuration) do |record, attr_name, value|
-          record.errors.add(attr_name, configuration[:message] % value) if enum.include?(value)
+          if enum.include?(value)
+            record.errors.add(attr_name, :exclusion, :default => configuration[:message], :value => value) 
+          end
         end
       end
     end
diff --git a/activemodel/lib/active_model/validations/format.rb b/activemodel/lib/active_model/validations/format.rb
index 1320ef646a..c71567b993 100644
--- a/activemodel/lib/active_model/validations/format.rb
+++ b/activemodel/lib/active_model/validations/format.rb
@@ -13,11 +13,11 @@ module ActiveModel
       # A regular expression must be provided or else an exception will be raised.
       #
       # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "is invalid")
-      # * <tt>:allow_nil</tt> - If set to +true+, skips this validation if the attribute is +nil+ (default is: +false+)
-      # * <tt>:allow_blank</tt> - If set to +true+, skips this validation if the attribute is blank (default is: +false+)
-      # * <tt>:with</tt> - The regular expression used to validate the format with (note: must be supplied!)
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>)
+      # * <tt>:message</tt> - A custom error message (default is: "is invalid").
+      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
+      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
+      # * <tt>:with</tt> - The regular expression used to validate the format with (note: must be supplied!).
+      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
@@ -25,13 +25,15 @@ module ActiveModel
       #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
       def validates_format_of(*attr_names)
-        configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save, :with => nil }
+        configuration = { :on => :save, :with => nil }
         configuration.update(attr_names.extract_options!)
 
         raise(ArgumentError, "A regular expression must be supplied as the :with option of the configuration hash") unless configuration[:with].is_a?(Regexp)
 
         validates_each(attr_names, configuration) do |record, attr_name, value|
-          record.errors.add(attr_name, configuration[:message]) unless value.to_s =~ configuration[:with]
+          unless value.to_s =~ configuration[:with]
+            record.errors.add(attr_name, :invalid, :default => configuration[:message], :value => value) 
+          end
         end
       end
     end
diff --git a/activemodel/lib/active_model/validations/inclusion.rb b/activemodel/lib/active_model/validations/inclusion.rb
index f288810d90..0cb8e44770 100644
--- a/activemodel/lib/active_model/validations/inclusion.rb
+++ b/activemodel/lib/active_model/validations/inclusion.rb
@@ -6,14 +6,14 @@ module ActiveModel
       #   class Person < ActiveRecord::Base
       #     validates_inclusion_of :gender, :in => %w( m f )
       #     validates_inclusion_of :age, :in => 0..99
-      #     validates_inclusion_of :format, :in => %w( jpg gif png ), :message => "extension %s is not included in the list"
+      #     validates_inclusion_of :format, :in => %w( jpg gif png ), :message => "extension {{value}} is not included in the list"
       #   end
       #
       # Configuration options:
-      # * <tt>:in</tt> - An enumerable object of available items
-      # * <tt>:message</tt> - Specifies a custom error message (default is: "is not included in the list")
-      # * <tt>:allow_nil</tt> - If set to +true+, skips this validation if the attribute is null (default is: +false+)
-      # * <tt>:allow_blank</tt> - If set to +true+, skips this validation if the attribute is blank (default is: +false+)
+      # * <tt>:in</tt> - An enumerable object of available items.
+      # * <tt>:message</tt> - Specifies a custom error message (default is: "is not included in the list").
+      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
+      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
@@ -21,7 +21,7 @@ module ActiveModel
       #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
       def validates_inclusion_of(*attr_names)
-        configuration = { :message => ActiveRecord::Errors.default_error_messages[:inclusion], :on => :save }
+        configuration = { :on => :save }
         configuration.update(attr_names.extract_options!)
 
         enum = configuration[:in] || configuration[:within]
@@ -29,7 +29,9 @@ module ActiveModel
         raise(ArgumentError, "An object with the method include? is required must be supplied as the :in option of the configuration hash") unless enum.respond_to?(:include?)
 
         validates_each(attr_names, configuration) do |record, attr_name, value|
-          record.errors.add(attr_name, configuration[:message] % value) unless enum.include?(value)
+          unless enum.include?(value)
+            record.errors.add(attr_name, :inclusion, :default => configuration[:message], :value => value) 
+          end
         end
       end
     end
diff --git a/activemodel/lib/active_model/validations/length.rb b/activemodel/lib/active_model/validations/length.rb
index 673ad33974..f6bb1f6d70 100644
--- a/activemodel/lib/active_model/validations/length.rb
+++ b/activemodel/lib/active_model/validations/length.rb
@@ -2,44 +2,46 @@ module ActiveModel
   module Validations
     module ClassMethods
       ALL_RANGE_OPTIONS = [ :is, :within, :in, :minimum, :maximum ].freeze
-    
+
       # Validates that the specified attribute matches the length restrictions supplied. Only one option can be used at a time:
       #
       #   class Person < ActiveRecord::Base
-      #     validates_length_of :first_name, :maximum => 30
-      #     validates_length_of :last_name, :maximum => 30, :message => "less than %d if you don't mind"
+      #     validates_length_of :first_name, :maximum=>30
+      #     validates_length_of :last_name, :maximum=>30, :message=>"less than {{count}} if you don't mind"
       #     validates_length_of :fax, :in => 7..32, :allow_nil => true
       #     validates_length_of :phone, :in => 7..32, :allow_blank => true
       #     validates_length_of :user_name, :within => 6..20, :too_long => "pick a shorter name", :too_short => "pick a longer name"
-      #     validates_length_of :fav_bra_size, :minimum => 1, :too_short => "please enter at least %d character"
-      #     validates_length_of :smurf_leader, :is => 4, :message => "papa is spelled with %d characters... don't play me."
+      #     validates_length_of :fav_bra_size, :minimum => 1, :too_short => "please enter at least {{count}} character"
+      #     validates_length_of :smurf_leader, :is => 4, :message => "papa is spelled with {{count}} characters... don't play me."
+      #     validates_length_of :essay, :minimum => 100, :too_short => "Your essay must be at least {{count}} words."), :tokenizer => lambda {|str| str.scan(/\w+/) }
       #   end
       #
       # Configuration options:
-      # * <tt>:minimum</tt> - The minimum size of the attribute
-      # * <tt>:maximum</tt> - The maximum size of the attribute
-      # * <tt>:is</tt> - The exact size of the attribute
-      # * <tt>:within</tt> - A range specifying the minimum and maximum size of the attribute
-      # * <tt>:in</tt> - A synonym (or alias) for <tt>:within</tt>
+      # * <tt>:minimum</tt> - The minimum size of the attribute.
+      # * <tt>:maximum</tt> - The maximum size of the attribute.
+      # * <tt>:is</tt> - The exact size of the attribute.
+      # * <tt>:within</tt> - A range specifying the minimum and maximum size of the attribute.
+      # * <tt>:in</tt> - A synonym(or alias) for <tt>:within</tt>.
       # * <tt>:allow_nil</tt> - Attribute may be +nil+; skip validation.
       # * <tt>:allow_blank</tt> - Attribute may be blank; skip validation.
-      # * <tt>:too_long</tt> - The error message if the attribute goes over the maximum (default is: "is too long (maximum is %d characters)")
-      # * <tt>:too_short</tt> - The error message if the attribute goes under the minimum (default is: "is too short (min is %d characters)")
-      # * <tt>:wrong_length</tt> - The error message if using the <tt>:is</tt> method and the attribute is the wrong size (default is: "is the wrong length (should be %d characters)")
-      # * <tt>:message</tt> - The error message to use for a <tt>:minimum</tt>, <tt>:maximum</tt>, or <tt>:is</tt> violation.  An alias of the appropriate <tt>:too_long</tt>/<tt>too_short</tt>/<tt>wrong_length</tt> message
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>)
+      # * <tt>:too_long</tt> - The error message if the attribute goes over the maximum (default is: "is too long (maximum is {{count}} characters)").
+      # * <tt>:too_short</tt> - The error message if the attribute goes under the minimum (default is: "is too short (min is {{count}} characters)").
+      # * <tt>:wrong_length</tt> - The error message if using the <tt>:is</tt> method and the attribute is the wrong size (default is: "is the wrong length (should be {{count}} characters)").
+      # * <tt>:message</tt> - The error message to use for a <tt>:minimum</tt>, <tt>:maximum</tt>, or <tt>:is</tt> violation.  An alias of the appropriate <tt>too_long</tt>/<tt>too_short</tt>/<tt>wrong_length</tt> message.
+      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
       # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
+      # * <tt>:tokenizer</tt> - Specifies how to split up the attribute string. (e.g. <tt>:tokenizer => lambda {|str| str.scan(/\w+/)}</tt> to
+      #   count words as in above example.)
+      #   Defaults to <tt>lambda{ |value| value.split(//) }</tt> which counts individual characters.
       def validates_length_of(*attrs)
         # Merge given options with defaults.
         options = {
-          :too_long     => ActiveRecord::Errors.default_error_messages[:too_long],
-          :too_short    => ActiveRecord::Errors.default_error_messages[:too_short],
-          :wrong_length => ActiveRecord::Errors.default_error_messages[:wrong_length]
+          :tokenizer => lambda {|value| value.split(//)}
         }.merge(DEFAULT_VALIDATION_OPTIONS)
         options.update(attrs.extract_options!.symbolize_keys)
 
@@ -57,35 +59,33 @@ module ActiveModel
         # Get range option and value.
         option = range_options.first
         option_value = options[range_options.first]
+        key = {:is => :wrong_length, :minimum => :too_short, :maximum => :too_long}[option]
+        custom_message = options[:message] || options[key]
 
         case option
-          when :within, :in
-            raise ArgumentError, ":#{option} must be a Range" unless option_value.is_a?(Range)
-
-            too_short = options[:too_short] % option_value.begin
-            too_long  = options[:too_long]  % option_value.end
+        when :within, :in
+          raise ArgumentError, ":#{option} must be a Range" unless option_value.is_a?(Range)
 
-            validates_each(attrs, options) do |record, attr, value|
-              value = value.split(//) if value.kind_of?(String)
-              if value.nil? or value.size < option_value.begin
-                record.errors.add(attr, too_short)
-              elsif value.size > option_value.end
-                record.errors.add(attr, too_long)
-              end
+          validates_each(attrs, options) do |record, attr, value|
+            value = options[:tokenizer].call(value) if value.kind_of?(String)
+            if value.nil? or value.size < option_value.begin
+              record.errors.add(attr, :too_short, :default => custom_message || options[:too_short], :count => option_value.begin)
+            elsif value.size > option_value.end
+              record.errors.add(attr, :too_long, :default => custom_message || options[:too_long], :count => option_value.end)
             end
-          when :is, :minimum, :maximum
-            raise ArgumentError, ":#{option} must be a nonnegative Integer" unless option_value.is_a?(Integer) and option_value >= 0
-
-            # Declare different validations per option.
-            validity_checks = { :is => "==", :minimum => ">=", :maximum => "<=" }
-            message_options = { :is => :wrong_length, :minimum => :too_short, :maximum => :too_long }
+          end
+        when :is, :minimum, :maximum
+          raise ArgumentError, ":#{option} must be a nonnegative Integer" unless option_value.is_a?(Integer) and option_value >= 0
 
-            message = (options[:message] || options[message_options[option]]) % option_value
+          # Declare different validations per option.
+          validity_checks = { :is => "==", :minimum => ">=", :maximum => "<=" }
 
-            validates_each(attrs, options) do |record, attr, value|
-              value = value.split(//) if value.kind_of?(String)
-              record.errors.add(attr, message) unless !value.nil? and value.size.method(validity_checks[option])[option_value]
+          validates_each(attrs, options) do |record, attr, value|
+            value = options[:tokenizer].call(value) if value.kind_of?(String)
+            unless !value.nil? and value.size.method(validity_checks[option])[option_value]
+              record.errors.add(attr, key, :default => custom_message, :count => option_value) 
             end
+          end
         end
       end
 
diff --git a/activemodel/lib/active_model/validations/numericality.rb b/activemodel/lib/active_model/validations/numericality.rb
index 92ca5f4082..d8e3470304 100644
--- a/activemodel/lib/active_model/validations/numericality.rb
+++ b/activemodel/lib/active_model/validations/numericality.rb
@@ -5,10 +5,9 @@ module ActiveModel
                                   :equal_to => '==', :less_than => '<', :less_than_or_equal_to => '<=',
                                   :odd => 'odd?', :even => 'even?' }.freeze
 
-
       # Validates whether the value of the specified attribute is numeric by trying to convert it to
-      # a float with Kernel.Float (if <tt>integer</tt> is false) or applying it to the regular expression
-      # <tt>/\A[\+\-]?\d+\Z/</tt> (if <tt>integer</tt> is true).
+      # a float with Kernel.Float (if <tt>only_integer</tt> is false) or applying it to the regular expression
+      # <tt>/\A[\+\-]?\d+\Z/</tt> (if <tt>only_integer</tt> is set to true).
       #
       #   class Person < ActiveRecord::Base
       #     validates_numericality_of :value, :on => :create
@@ -50,15 +49,15 @@ module ActiveModel
 
           if configuration[:only_integer]
             unless raw_value.to_s =~ /\A[+-]?\d+\Z/
-              record.errors.add(attr_name, configuration[:message] || ActiveRecord::Errors.default_error_messages[:not_a_number])
+              record.errors.add(attr_name, :not_a_number, :value => raw_value, :default => configuration[:message])
               next
             end
             raw_value = raw_value.to_i
           else
-           begin
-              raw_value = Kernel.Float(raw_value.to_s)
+            begin
+              raw_value = Kernel.Float(raw_value)
             rescue ArgumentError, TypeError
-              record.errors.add(attr_name, configuration[:message] || ActiveRecord::Errors.default_error_messages[:not_a_number])
+              record.errors.add(attr_name, :not_a_number, :value => raw_value, :default => configuration[:message])
               next
             end
           end
@@ -66,11 +65,13 @@ module ActiveModel
           numericality_options.each do |option|
             case option
               when :odd, :even
-                record.errors.add(attr_name, configuration[:message] || ActiveRecord::Errors.default_error_messages[option]) unless raw_value.to_i.method(ALL_NUMERICALITY_CHECKS[option])[]
+                unless raw_value.to_i.method(ALL_NUMERICALITY_CHECKS[option])[]
+                  record.errors.add(attr_name, option, :value => raw_value, :default => configuration[:message]) 
+                end
               else
-                message = configuration[:message] || ActiveRecord::Errors.default_error_messages[option]
-                message = message % configuration[option] if configuration[option]
-                record.errors.add(attr_name, message) unless raw_value.method(ALL_NUMERICALITY_CHECKS[option])[configuration[option]]
+                unless raw_value.method(ALL_NUMERICALITY_CHECKS[option])[configuration[option]]
+                  record.errors.add(attr_name, option, :default => configuration[:message], :value => raw_value, :count => configuration[option])
+                end
             end
           end
         end
diff --git a/activemodel/lib/active_model/validations/presence.rb b/activemodel/lib/active_model/validations/presence.rb
index 62e466901b..4fd60621cd 100644
--- a/activemodel/lib/active_model/validations/presence.rb
+++ b/activemodel/lib/active_model/validations/presence.rb
@@ -7,28 +7,26 @@ module ActiveModel
       #     validates_presence_of :first_name
       #   end
       #
-      # The +first_name+ attribute must be in the object and it cannot be blank.
+      # The first_name attribute must be in the object and it cannot be blank.
       #
-      # If you want to validate the presence of a boolean field (where the real values are +true+ and +false+),
-      # you will want to use
+      # If you want to validate the presence of a boolean field (where the real values are true and false),
+      # you will want to use <tt>validates_inclusion_of :field_name, :in => [true, false]</tt>.
       #
-      #   validates_inclusion_of :field_name, :in => [true, false]
-      #
-      # This is due to the way Object#blank? handles boolean values:
-      #
-      #   false.blank? # => true
+      # This is due to the way Object#blank? handles boolean values: <tt>false.blank? # => true</tt>.
       #
       # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "can't be blank")
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>)
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
+      # * <tt>message</tt> - A custom error message (default is: "can't be blank").
+      # * <tt>on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, 
+      #   <tt>:update</tt>).
+      # * <tt>if</tt> - Specifies a method, proc or string to call to determine if the validation should
+      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).
+      #   The method, proc or string should return or evaluate to a true or false value.
+      # * <tt>unless</tt> - Specifies a method, proc or string to call to determine if the validation should
+      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).
+      #   The method, proc or string should return or evaluate to a true or false value.
+      #
       def validates_presence_of(*attr_names)
-        configuration = { :message => ActiveRecord::Errors.default_error_messages[:blank], :on => :save }
+        configuration = { :on => :save }
         configuration.update(attr_names.extract_options!)
 
         # can't use validates_each here, because it cannot cope with nonexistent attributes,
diff --git a/activemodel/lib/active_model/validations/uniqueness.rb b/activemodel/lib/active_model/validations/uniqueness.rb
index 593d2cfd54..37beac863f 100644
--- a/activemodel/lib/active_model/validations/uniqueness.rb
+++ b/activemodel/lib/active_model/validations/uniqueness.rb
@@ -18,24 +18,84 @@ module ActiveModel
       # When the record is created, a check is performed to make sure that no record exists in the database with the given value for the specified
       # attribute (that maps to a column). When the record is updated, the same check is made but disregarding the record itself.
       #
-      # Because this check is performed outside the database there is still a chance that duplicate values
-      # will be inserted in two parallel transactions.  To guarantee against this you should create a 
-      # unique index on the field. See +add_index+ for more information.
-      #
       # Configuration options:
-      # * <tt>:message</tt> - Specifies a custom error message (default is: "has already been taken")
+      # * <tt>:message</tt> - Specifies a custom error message (default is: "has already been taken").
       # * <tt>:scope</tt> - One or more columns by which to limit the scope of the uniqueness constraint.
-      # * <tt>:case_sensitive</tt> - Looks for an exact match.  Ignored by non-text columns (+true+ by default).
-      # * <tt>:allow_nil</tt> - If set to +true+, skips this validation if the attribute is +nil+ (default is: +false+)
-      # * <tt>:allow_blank</tt> - If set to +true+, skips this validation if the attribute is blank (default is: +false+)
+      # * <tt>:case_sensitive</tt> - Looks for an exact match. Ignored by non-text columns (+true+ by default).
+      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
+      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
       # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
       # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
       #   method, proc or string should return or evaluate to a true or false value.
+      #
+      # === Concurrency and integrity
+      #
+      # Using this validation method in conjunction with ActiveRecord::Base#save
+      # does not guarantee the absence of duplicate record insertions, because
+      # uniqueness checks on the application level are inherently prone to race
+      # conditions. For example, suppose that two users try to post a Comment at
+      # the same time, and a Comment's title must be unique. At the database-level,
+      # the actions performed by these users could be interleaved in the following manner:
+      #
+      #               User 1                 |               User 2
+      #  ------------------------------------+--------------------------------------
+      #  # User 1 checks whether there's     |
+      #  # already a comment with the title  |
+      #  # 'My Post'. This is not the case.  |
+      #  SELECT * FROM comments              |
+      #  WHERE title = 'My Post'             |
+      #                                      |
+      #                                      | # User 2 does the same thing and also
+      #                                      | # infers that his title is unique.
+      #                                      | SELECT * FROM comments
+      #                                      | WHERE title = 'My Post'
+      #                                      |
+      #  # User 1 inserts his comment.       |
+      #  INSERT INTO comments                |
+      #  (title, content) VALUES             |
+      #  ('My Post', 'hi!')                  |
+      #                                      |
+      #                                      | # User 2 does the same thing.
+      #                                      | INSERT INTO comments
+      #                                      | (title, content) VALUES
+      #                                      | ('My Post', 'hello!')
+      #                                      |
+      #                                      | # ^^^^^^
+      #                                      | # Boom! We now have a duplicate
+      #                                      | # title!
+      #
+      # This could even happen if you use transactions with the 'serializable'
+      # isolation level. There are several ways to get around this problem:
+      # - By locking the database table before validating, and unlocking it after
+      #   saving. However, table locking is very expensive, and thus not
+      #   recommended.
+      # - By locking a lock file before validating, and unlocking it after saving.
+      #   This does not work if you've scaled your Rails application across
+      #   multiple web servers (because they cannot share lock files, or cannot
+      #   do that efficiently), and thus not recommended.
+      # - Creating a unique index on the field, by using
+      #   ActiveRecord::ConnectionAdapters::SchemaStatements#add_index. In the
+      #   rare case that a race condition occurs, the database will guarantee
+      #   the field's uniqueness.
+      #   
+      #   When the database catches such a duplicate insertion,
+      #   ActiveRecord::Base#save will raise an ActiveRecord::StatementInvalid
+      #   exception. You can either choose to let this error propagate (which
+      #   will result in the default Rails exception page being shown), or you
+      #   can catch it and restart the transaction (e.g. by telling the user
+      #   that the title already exists, and asking him to re-enter the title).
+      #   This technique is also known as optimistic concurrency control:
+      #   http://en.wikipedia.org/wiki/Optimistic_concurrency_control
+      #   
+      #   Active Record currently provides no way to distinguish unique
+      #   index constraint errors from other types of database errors, so you
+      #   will have to parse the (database-specific) exception message to detect
+      #   such a case.
       def validates_uniqueness_of(*attr_names)
-        configuration = { :message => ActiveRecord::Errors.default_error_messages[:taken] }
+        configuration = { :case_sensitive => true }
         configuration.update(attr_names.extract_options!)
 
         validates_each(attr_names,configuration) do |record, attr_name, value|
@@ -53,20 +113,31 @@ module ActiveModel
           # class (which has a database table to query from).
           finder_class = class_hierarchy.detect { |klass| !klass.abstract_class? }
 
-          if value.nil? || (configuration[:case_sensitive] || !finder_class.columns_hash[attr_name.to_s].text?)
-            condition_sql = "#{record.class.quoted_table_name}.#{attr_name} #{attribute_condition(value)}"
+          column = finder_class.columns_hash[attr_name.to_s]
+
+          if value.nil?
+            comparison_operator = "IS ?"
+          elsif column.text?
+            comparison_operator = "#{connection.case_sensitive_equality_operator} ?"
+            value = column.limit ? value.to_s[0, column.limit] : value.to_s
+          else
+            comparison_operator = "= ?"
+          end
+
+          sql_attribute = "#{record.class.quoted_table_name}.#{connection.quote_column_name(attr_name)}"
+
+          if value.nil? || (configuration[:case_sensitive] || !column.text?)
+            condition_sql = "#{sql_attribute} #{comparison_operator}"
             condition_params = [value]
           else
-            # sqlite has case sensitive SELECT query, while MySQL/Postgresql don't.
-            # Hence, this is needed only for sqlite.
-            condition_sql = "LOWER(#{record.class.quoted_table_name}.#{attr_name}) #{attribute_condition(value)}"
-            condition_params = [value.downcase]
+            condition_sql = "LOWER(#{sql_attribute}) #{comparison_operator}"
+            condition_params = [value.mb_chars.downcase]
           end
 
           if scope = configuration[:scope]
             Array(scope).map do |scope_item|
               scope_value = record.send(scope_item)
-              condition_sql << " AND #{record.class.quoted_table_name}.#{scope_item} #{attribute_condition(scope_value)}"
+              condition_sql << " AND " << attribute_condition("#{record.class.quoted_table_name}.#{scope_item}", scope_value)
               condition_params << scope_value
             end
           end
@@ -76,26 +147,10 @@ module ActiveModel
             condition_params << record.send(:id)
           end
 
-          results = finder_class.with_exclusive_scope do
-            connection.select_all(
-              construct_finder_sql(
-                :select     => attr_name,
-                :from       => finder_class.quoted_table_name,
-                :conditions => [condition_sql, *condition_params]
-              )
-            )
-          end
-
-          unless results.length.zero?
-            found = true
-
-            # As MySQL/Postgres don't have case sensitive SELECT queries, we try to find duplicate
-            # column in ruby when case sensitive option
-            if configuration[:case_sensitive] && finder_class.columns_hash[attr_name.to_s].text?
-              found = results.any? { |a| a[attr_name.to_s] == value }
+          finder_class.with_exclusive_scope do
+            if finder_class.exists?([condition_sql, *condition_params])
+              record.errors.add(attr_name, :taken, :default => configuration[:message], :value => value)
             end
-
-            record.errors.add(attr_name, configuration[:message]) if found
           end
         end
       end
diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 2f8c5c712f..104d3b2917 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -31,6 +31,15 @@ rescue LoadError
   end
 end
 
+begin
+  require 'active_model'
+rescue LoadError
+  $:.unshift "#{File.dirname(__FILE__)}/../../activemodel/lib"
+  require 'active_model'
+else
+  
+end
+
 module ActiveRecord
   # TODO: Review explicit loads to see if they will automatically be handled by the initilizer.
   def self.load_all!
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index 741aa2acbe..4a03585b18 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -251,7 +251,7 @@ module ActiveRecord
           unless association.marked_for_destruction?
             association.errors.each do |attribute, message|
               attribute = "#{reflection.name}_#{attribute}"
-              errors.add(attribute, message) unless errors.on(attribute)
+              errors[attribute] << message if errors[attribute].empty?
             end
           end
         else
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 2a5385119d..bf7fd904b1 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -3136,7 +3136,7 @@ module ActiveRecord #:nodoc:
 
   Base.class_eval do
     extend QueryCache::ClassMethods
-    include Validations
+    include ::ActiveModel::Validations, Validations
     include Locking::Optimistic, Locking::Pessimistic
     include AttributeMethods
     include Dirty
diff --git a/activerecord/lib/active_record/validations.rb b/activerecord/lib/active_record/validations.rb
index d2d12b80c9..a7043516a7 100644
--- a/activerecord/lib/active_record/validations.rb
+++ b/activerecord/lib/active_record/validations.rb
@@ -14,971 +14,17 @@ module ActiveRecord
     end
   end
 
-  # Active Record validation is reported to and from this object, which is used by Base#save to
-  # determine whether the object is in a valid state to be saved. See usage example in Validations.
-  class Errors
-    include Enumerable
-    
-    class << self
-      def default_error_messages
-        ActiveSupport::Deprecation.warn("ActiveRecord::Errors.default_error_messages has been deprecated. Please use I18n.translate('activerecord.errors.messages').")
-        I18n.translate 'activerecord.errors.messages'
-      end
-    end
-
-    def initialize(base) # :nodoc:
-      @base, @errors = base, {}
-    end
-
-    # Adds an error to the base object instead of any particular attribute. This is used
-    # to report errors that don't tie to any specific attribute, but rather to the object
-    # as a whole. These error messages don't get prepended with any field name when iterating
-    # with +each_full+, so they should be complete sentences.
-    def add_to_base(msg)
-      add(:base, msg)
-    end
-
-    # Adds an error message (+messsage+) to the +attribute+, which will be returned on a call to <tt>on(attribute)</tt>
-    # for the same attribute and ensure that this error object returns false when asked if <tt>empty?</tt>. More than one
-    # error can be added to the same +attribute+ in which case an array will be returned on a call to <tt>on(attribute)</tt>.
-    # If no +messsage+ is supplied, :invalid is assumed.
-    # If +message+ is a Symbol, it will be translated, using the appropriate scope (see translate_error).
-    def add(attribute, message = nil, options = {})
-      message ||= :invalid
-      message = generate_message(attribute, message, options) if message.is_a?(Symbol)
-      @errors[attribute.to_s] ||= []
-      @errors[attribute.to_s] << message
-    end
-
-    # Will add an error message to each of the attributes in +attributes+ that is empty.
-    def add_on_empty(attributes, custom_message = nil)
-      for attr in [attributes].flatten
-        value = @base.respond_to?(attr.to_s) ? @base.send(attr.to_s) : @base[attr.to_s]
-        is_empty = value.respond_to?(:empty?) ? value.empty? : false
-        add(attr, :empty, :default => custom_message) unless !value.nil? && !is_empty
-      end
-    end
-
-    # Will add an error message to each of the attributes in +attributes+ that is blank (using Object#blank?).
-    def add_on_blank(attributes, custom_message = nil)
-      for attr in [attributes].flatten
-        value = @base.respond_to?(attr.to_s) ? @base.send(attr.to_s) : @base[attr.to_s]
-        add(attr, :blank, :default => custom_message) if value.blank?
-      end
-    end
-    
-    # Translates an error message in it's default scope (<tt>activerecord.errrors.messages</tt>).
-    # Error messages are first looked up in <tt>models.MODEL.attributes.ATTRIBUTE.MESSAGE</tt>, if it's not there, 
-    # it's looked up in <tt>models.MODEL.MESSAGE</tt> and if that is not there it returns the translation of the 
-    # default message (e.g. <tt>activerecord.errors.messages.MESSAGE</tt>). The translated model name, 
-    # translated attribute name and the value are available for interpolation.
-    #
-    # When using inheritence in your models, it will check all the inherited models too, but only if the model itself
-    # hasn't been found. Say you have <tt>class Admin < User; end</tt> and you wanted the translation for the <tt>:blank</tt>
-    # error +message+ for the <tt>title</tt> +attribute+, it looks for these translations:
-    # 
-    # <ol>
-    # <li><tt>activerecord.errors.models.admin.attributes.title.blank</tt></li>
-    # <li><tt>activerecord.errors.models.admin.blank</tt></li>
-    # <li><tt>activerecord.errors.models.user.attributes.title.blank</tt></li>
-    # <li><tt>activerecord.errors.models.user.blank</tt></li>
-    # <li><tt>activerecord.errors.messages.blank</tt></li>
-    # <li>any default you provided through the +options+ hash (in the activerecord.errors scope)</li>
-    # </ol>
-    def generate_message(attribute, message = :invalid, options = {})
-
-      message, options[:default] = options[:default], message if options[:default].is_a?(Symbol)
-
-      defaults = @base.class.self_and_descendants_from_active_record.map do |klass|
-        [ :"models.#{klass.name.underscore}.attributes.#{attribute}.#{message}", 
-          :"models.#{klass.name.underscore}.#{message}" ]
-      end
-      
-      defaults << options.delete(:default)
-      defaults = defaults.compact.flatten << :"messages.#{message}"
-
-      key = defaults.shift
-      value = @base.respond_to?(attribute) ? @base.send(attribute) : nil
-
-      options = { :default => defaults,
-        :model => @base.class.human_name,
-        :attribute => @base.class.human_attribute_name(attribute.to_s),
-        :value => value,
-        :scope => [:activerecord, :errors]
-      }.merge(options)
-
-      I18n.translate(key, options)
-    end
-
-    # Returns true if the specified +attribute+ has errors associated with it.
-    #
-    #   class Company < ActiveRecord::Base
-    #     validates_presence_of :name, :address, :email
-    #     validates_length_of :name, :in => 5..30
-    #   end
-    #
-    #   company = Company.create(:address => '123 First St.')
-    #   company.errors.invalid?(:name)      # => true
-    #   company.errors.invalid?(:address)   # => false
-    def invalid?(attribute)
-      !@errors[attribute.to_s].nil?
-    end
-
-    # Returns +nil+, if no errors are associated with the specified +attribute+.
-    # Returns the error message, if one error is associated with the specified +attribute+.
-    # Returns an array of error messages, if more than one error is associated with the specified +attribute+.
-    #
-    #   class Company < ActiveRecord::Base
-    #     validates_presence_of :name, :address, :email
-    #     validates_length_of :name, :in => 5..30
-    #   end
-    #
-    #   company = Company.create(:address => '123 First St.')
-    #   company.errors.on(:name)      # => ["is too short (minimum is 5 characters)", "can't be blank"]
-    #   company.errors.on(:email)     # => "can't be blank"
-    #   company.errors.on(:address)   # => nil
-    def on(attribute)
-      errors = @errors[attribute.to_s]
-      return nil if errors.nil?
-      errors.size == 1 ? errors.first : errors
-    end
-
-    alias :[] :on
-
-    # Returns errors assigned to the base object through +add_to_base+ according to the normal rules of <tt>on(attribute)</tt>.
-    def on_base
-      on(:base)
-    end
-
-    # Yields each attribute and associated message per error added.
-    #
-    #   class Company < ActiveRecord::Base
-    #     validates_presence_of :name, :address, :email
-    #     validates_length_of :name, :in => 5..30
-    #   end
-    #
-    #   company = Company.create(:address => '123 First St.')
-    #   company.errors.each{|attr,msg| puts "#{attr} - #{msg}" }
-    #   # => name - is too short (minimum is 5 characters)
-    #   #    name - can't be blank
-    #   #    address - can't be blank
-    def each
-      @errors.each_key { |attr| @errors[attr].each { |msg| yield attr, msg } }
-    end
-
-    # Yields each full error message added. So <tt>Person.errors.add("first_name", "can't be empty")</tt> will be returned
-    # through iteration as "First name can't be empty".
-    #
-    #   class Company < ActiveRecord::Base
-    #     validates_presence_of :name, :address, :email
-    #     validates_length_of :name, :in => 5..30
-    #   end
-    #
-    #   company = Company.create(:address => '123 First St.')
-    #   company.errors.each_full{|msg| puts msg }
-    #   # => Name is too short (minimum is 5 characters)
-    #   #    Name can't be blank
-    #   #    Address can't be blank
-    def each_full
-      full_messages.each { |msg| yield msg }
-    end
-
-    # Returns all the full error messages in an array.
-    #
-    #   class Company < ActiveRecord::Base
-    #     validates_presence_of :name, :address, :email
-    #     validates_length_of :name, :in => 5..30
-    #   end
-    #
-    #   company = Company.create(:address => '123 First St.')
-    #   company.errors.full_messages # =>
-    #     ["Name is too short (minimum is 5 characters)", "Name can't be blank", "Address can't be blank"]
-    def full_messages(options = {})
-      full_messages = []
-
-      @errors.each_key do |attr|
-        @errors[attr].each do |message|
-          next unless message
-
-          if attr == "base"
-            full_messages << message
-          else
-            attr_name = @base.class.human_attribute_name(attr)
-            full_messages << attr_name + I18n.t('activerecord.errors.format.separator', :default => ' ') + message
-          end
-        end
-      end
-      full_messages
-    end 
-
-    # Returns true if no errors have been added.
-    def empty?
-      @errors.empty?
-    end
-
-    # Removes all errors that have been added.
-    def clear
-      @errors = {}
-    end
-
-    # Returns the total number of errors added. Two errors added to the same attribute will be counted as such.
-    def size
-      @errors.values.inject(0) { |error_count, attribute| error_count + attribute.size }
-    end
-
-    alias_method :count, :size
-    alias_method :length, :size
-
-    # Returns an XML representation of this error object.
-    #
-    #   class Company < ActiveRecord::Base
-    #     validates_presence_of :name, :address, :email
-    #     validates_length_of :name, :in => 5..30
-    #   end
-    #
-    #   company = Company.create(:address => '123 First St.')
-    #   company.errors.to_xml
-    #   # =>  <?xml version="1.0" encoding="UTF-8"?>
-    #   #     <errors>
-    #   #       <error>Name is too short (minimum is 5 characters)</error>
-    #   #       <error>Name can't be blank</error>
-    #   #       <error>Address can't be blank</error>
-    #   #     </errors>
-    def to_xml(options={})
-      options[:root] ||= "errors"
-      options[:indent] ||= 2
-      options[:builder] ||= Builder::XmlMarkup.new(:indent => options[:indent])
-
-      options[:builder].instruct! unless options.delete(:skip_instruct)
-      options[:builder].errors do |e|
-        full_messages.each { |msg| e.error(msg) }
-      end
-    end
-    
-  end
-
-
-  # Please do have a look at ActiveRecord::Validations::ClassMethods for a higher level of validations.
-  #
-  # Active Records implement validation by overwriting Base#validate (or the variations, +validate_on_create+ and
-  # +validate_on_update+). Each of these methods can inspect the state of the object, which usually means ensuring
-  # that a number of attributes have a certain value (such as not empty, within a given range, matching a certain regular expression).
-  #
-  # Example:
-  #
-  #   class Person < ActiveRecord::Base
-  #     protected
-  #       def validate
-  #         errors.add_on_empty %w( first_name last_name )
-  #         errors.add("phone_number", "has invalid format") unless phone_number =~ /[0-9]*/
-  #       end
-  #
-  #       def validate_on_create # is only run the first time a new object is saved
-  #         unless valid_discount?(membership_discount)
-  #           errors.add("membership_discount", "has expired")
-  #         end
-  #       end
-  #
-  #       def validate_on_update
-  #         errors.add_to_base("No changes have occurred") if unchanged_attributes?
-  #       end
-  #   end
-  #
-  #   person = Person.new("first_name" => "David", "phone_number" => "what?")
-  #   person.save                         # => false (and doesn't do the save)
-  #   person.errors.empty?                # => false
-  #   person.errors.count                 # => 2
-  #   person.errors.on "last_name"        # => "can't be empty"
-  #   person.errors.on "phone_number"     # => "has invalid format"
-  #   person.errors.each_full { |msg| puts msg }
-  #                                       # => "Last name can't be empty\n" +
-  #                                       #    "Phone number has invalid format"
-  #
-  #   person.attributes = { "last_name" => "Heinemeier", "phone_number" => "555-555" }
-  #   person.save # => true (and person is now saved in the database)
-  #
-  # An Errors object is automatically created for every Active Record.
   module Validations
-    VALIDATIONS = %w( validate validate_on_create validate_on_update )
-
     def self.included(base) # :nodoc:
       base.extend ClassMethods
+
       base.class_eval do
         alias_method_chain :save, :validation
         alias_method_chain :save!, :validation
       end
-
-      base.send :include, ActiveSupport::Callbacks
-      base.define_callbacks *VALIDATIONS
     end
 
-    # Active Record classes can implement validations in several ways. The highest level, easiest to read,
-    # and recommended approach is to use the declarative <tt>validates_..._of</tt> class methods (and
-    # +validates_associated+) documented below. These are sufficient for most model validations.
-    #
-    # Slightly lower level is +validates_each+. It provides some of the same options as the purely declarative
-    # validation methods, but like all the lower-level approaches it requires manually adding to the errors collection
-    # when the record is invalid.
-    #
-    # At a yet lower level, a model can use the class methods +validate+, +validate_on_create+ and +validate_on_update+
-    # to add validation methods or blocks. These are ActiveSupport::Callbacks and follow the same rules of inheritance
-    # and chaining.
-    #
-    # The lowest level style is to define the instance methods +validate+, +validate_on_create+ and +validate_on_update+
-    # as documented in ActiveRecord::Validations.
-    #
-    # == +validate+, +validate_on_create+ and +validate_on_update+ Class Methods
-    #
-    # Calls to these methods add a validation method or block to the class. Again, this approach is recommended
-    # only when the higher-level methods documented below (<tt>validates_..._of</tt> and +validates_associated+) are
-    # insufficient to handle the required validation.
-    #
-    # This can be done with a symbol pointing to a method:
-    #
-    #   class Comment < ActiveRecord::Base
-    #     validate :must_be_friends
-    #
-    #     def must_be_friends
-    #       errors.add_to_base("Must be friends to leave a comment") unless commenter.friend_of?(commentee)
-    #     end
-    #   end
-    #
-    # Or with a block which is passed the current record to be validated:
-    #
-    #   class Comment < ActiveRecord::Base
-    #     validate do |comment|
-    #       comment.must_be_friends
-    #     end
-    #
-    #     def must_be_friends
-    #       errors.add_to_base("Must be friends to leave a comment") unless commenter.friend_of?(commentee)
-    #     end
-    #   end
-    #
-    # This usage applies to +validate_on_create+ and +validate_on_update+ as well.
     module ClassMethods
-      DEFAULT_VALIDATION_OPTIONS = {
-        :on => :save,
-        :allow_nil => false,
-        :allow_blank => false,
-        :message => nil
-      }.freeze
-
-      ALL_RANGE_OPTIONS = [ :is, :within, :in, :minimum, :maximum ].freeze
-      ALL_NUMERICALITY_CHECKS = { :greater_than => '>', :greater_than_or_equal_to => '>=',
-                                  :equal_to => '==', :less_than => '<', :less_than_or_equal_to => '<=',
-                                  :odd => 'odd?', :even => 'even?' }.freeze
-
-      # Validates each attribute against a block.
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_each :first_name, :last_name do |record, attr, value|
-      #       record.errors.add attr, 'starts with z.' if value[0] == ?z
-      #     end
-      #   end
-      #
-      # Options:
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
-      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+.
-      # * <tt>:allow_blank</tt> - Skip validation if attribute is blank.
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      def validates_each(*attrs)
-        options = attrs.extract_options!.symbolize_keys
-        attrs   = attrs.flatten
-
-        # Declare the validation.
-        send(validation_method(options[:on] || :save), options) do |record|
-          attrs.each do |attr|
-            value = record.send(attr)
-            next if (value.nil? && options[:allow_nil]) || (value.blank? && options[:allow_blank])
-            yield record, attr, value
-          end
-        end
-      end
-
-      # Encapsulates the pattern of wanting to validate a password or email address field with a confirmation. Example:
-      #
-      #   Model:
-      #     class Person < ActiveRecord::Base
-      #       validates_confirmation_of :user_name, :password
-      #       validates_confirmation_of :email_address, :message => "should match confirmation"
-      #     end
-      #
-      #   View:
-      #     <%= password_field "person", "password" %>
-      #     <%= password_field "person", "password_confirmation" %>
-      #
-      # The added +password_confirmation+ attribute is virtual; it exists only as an in-memory attribute for validating the password.
-      # To achieve this, the validation adds accessors to the model for the confirmation attribute. NOTE: This check is performed
-      # only if +password_confirmation+ is not +nil+, and by default only on save. To require confirmation, make sure to add a presence
-      # check for the confirmation attribute:
-      #
-      #   validates_presence_of :password_confirmation, :if => :password_changed?
-      #
-      # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "doesn't match confirmation").
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      def validates_confirmation_of(*attr_names)
-        configuration = { :on => :save }
-        configuration.update(attr_names.extract_options!)
-
-        attr_accessor(*(attr_names.map { |n| "#{n}_confirmation" }))
-
-        validates_each(attr_names, configuration) do |record, attr_name, value|
-          unless record.send("#{attr_name}_confirmation").nil? or value == record.send("#{attr_name}_confirmation")
-            record.errors.add(attr_name, :confirmation, :default => configuration[:message]) 
-          end
-        end
-      end
-
-      # Encapsulates the pattern of wanting to validate the acceptance of a terms of service check box (or similar agreement). Example:
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_acceptance_of :terms_of_service
-      #     validates_acceptance_of :eula, :message => "must be abided"
-      #   end
-      #
-      # If the database column does not exist, the +terms_of_service+ attribute is entirely virtual. This check is
-      # performed only if +terms_of_service+ is not +nil+ and by default on save.
-      #
-      # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "must be accepted").
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
-      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+ (default is true).
-      # * <tt>:accept</tt> - Specifies value that is considered accepted.  The default value is a string "1", which
-      #   makes it easy to relate to an HTML checkbox. This should be set to +true+ if you are validating a database
-      #   column, since the attribute is typecast from "1" to +true+ before validation.
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      def validates_acceptance_of(*attr_names)
-        configuration = { :on => :save, :allow_nil => true, :accept => "1" }
-        configuration.update(attr_names.extract_options!)
-
-        db_cols = begin
-          column_names
-        rescue Exception # To ignore both statement and connection errors
-          []
-        end
-        names = attr_names.reject { |name| db_cols.include?(name.to_s) }
-        attr_accessor(*names)
-
-        validates_each(attr_names,configuration) do |record, attr_name, value|
-          unless value == configuration[:accept]
-            record.errors.add(attr_name, :accepted, :default => configuration[:message]) 
-          end
-        end
-      end
-
-      # Validates that the specified attributes are not blank (as defined by Object#blank?). Happens by default on save. Example:
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_presence_of :first_name
-      #   end
-      #
-      # The first_name attribute must be in the object and it cannot be blank.
-      #
-      # If you want to validate the presence of a boolean field (where the real values are true and false),
-      # you will want to use <tt>validates_inclusion_of :field_name, :in => [true, false]</tt>.
-      #
-      # This is due to the way Object#blank? handles boolean values: <tt>false.blank? # => true</tt>.
-      #
-      # Configuration options:
-      # * <tt>message</tt> - A custom error message (default is: "can't be blank").
-      # * <tt>on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, 
-      #   <tt>:update</tt>).
-      # * <tt>if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).
-      #   The method, proc or string should return or evaluate to a true or false value.
-      # * <tt>unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).
-      #   The method, proc or string should return or evaluate to a true or false value.
-      #
-      def validates_presence_of(*attr_names)
-        configuration = { :on => :save }
-        configuration.update(attr_names.extract_options!)
-
-        # can't use validates_each here, because it cannot cope with nonexistent attributes,
-        # while errors.add_on_empty can
-        send(validation_method(configuration[:on]), configuration) do |record|
-          record.errors.add_on_blank(attr_names, configuration[:message])
-        end
-      end
-
-      # Validates that the specified attribute matches the length restrictions supplied. Only one option can be used at a time:
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_length_of :first_name, :maximum=>30
-      #     validates_length_of :last_name, :maximum=>30, :message=>"less than {{count}} if you don't mind"
-      #     validates_length_of :fax, :in => 7..32, :allow_nil => true
-      #     validates_length_of :phone, :in => 7..32, :allow_blank => true
-      #     validates_length_of :user_name, :within => 6..20, :too_long => "pick a shorter name", :too_short => "pick a longer name"
-      #     validates_length_of :fav_bra_size, :minimum => 1, :too_short => "please enter at least {{count}} character"
-      #     validates_length_of :smurf_leader, :is => 4, :message => "papa is spelled with {{count}} characters... don't play me."
-      #     validates_length_of :essay, :minimum => 100, :too_short => "Your essay must be at least {{count}} words."), :tokenizer => lambda {|str| str.scan(/\w+/) }
-      #   end
-      #
-      # Configuration options:
-      # * <tt>:minimum</tt> - The minimum size of the attribute.
-      # * <tt>:maximum</tt> - The maximum size of the attribute.
-      # * <tt>:is</tt> - The exact size of the attribute.
-      # * <tt>:within</tt> - A range specifying the minimum and maximum size of the attribute.
-      # * <tt>:in</tt> - A synonym(or alias) for <tt>:within</tt>.
-      # * <tt>:allow_nil</tt> - Attribute may be +nil+; skip validation.
-      # * <tt>:allow_blank</tt> - Attribute may be blank; skip validation.
-      # * <tt>:too_long</tt> - The error message if the attribute goes over the maximum (default is: "is too long (maximum is {{count}} characters)").
-      # * <tt>:too_short</tt> - The error message if the attribute goes under the minimum (default is: "is too short (min is {{count}} characters)").
-      # * <tt>:wrong_length</tt> - The error message if using the <tt>:is</tt> method and the attribute is the wrong size (default is: "is the wrong length (should be {{count}} characters)").
-      # * <tt>:message</tt> - The error message to use for a <tt>:minimum</tt>, <tt>:maximum</tt>, or <tt>:is</tt> violation.  An alias of the appropriate <tt>too_long</tt>/<tt>too_short</tt>/<tt>wrong_length</tt> message.
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:tokenizer</tt> - Specifies how to split up the attribute string. (e.g. <tt>:tokenizer => lambda {|str| str.scan(/\w+/)}</tt> to
-      #   count words as in above example.)
-      #   Defaults to <tt>lambda{ |value| value.split(//) }</tt> which counts individual characters.
-      def validates_length_of(*attrs)
-        # Merge given options with defaults.
-        options = {
-          :tokenizer => lambda {|value| value.split(//)}
-        }.merge(DEFAULT_VALIDATION_OPTIONS)
-        options.update(attrs.extract_options!.symbolize_keys)
-
-        # Ensure that one and only one range option is specified.
-        range_options = ALL_RANGE_OPTIONS & options.keys
-        case range_options.size
-          when 0
-            raise ArgumentError, 'Range unspecified.  Specify the :within, :maximum, :minimum, or :is option.'
-          when 1
-            # Valid number of options; do nothing.
-          else
-            raise ArgumentError, 'Too many range options specified.  Choose only one.'
-        end
-
-        # Get range option and value.
-        option = range_options.first
-        option_value = options[range_options.first]
-        key = {:is => :wrong_length, :minimum => :too_short, :maximum => :too_long}[option]
-        custom_message = options[:message] || options[key]
-
-        case option
-          when :within, :in
-            raise ArgumentError, ":#{option} must be a Range" unless option_value.is_a?(Range)
-
-            validates_each(attrs, options) do |record, attr, value|
-              value = options[:tokenizer].call(value) if value.kind_of?(String)
-              if value.nil? or value.size < option_value.begin
-                record.errors.add(attr, :too_short, :default => custom_message || options[:too_short], :count => option_value.begin)
-              elsif value.size > option_value.end
-                record.errors.add(attr, :too_long, :default => custom_message || options[:too_long], :count => option_value.end)
-              end
-            end
-          when :is, :minimum, :maximum
-            raise ArgumentError, ":#{option} must be a nonnegative Integer" unless option_value.is_a?(Integer) and option_value >= 0
-
-            # Declare different validations per option.
-            validity_checks = { :is => "==", :minimum => ">=", :maximum => "<=" }
-
-            validates_each(attrs, options) do |record, attr, value|
-              value = options[:tokenizer].call(value) if value.kind_of?(String)
-              unless !value.nil? and value.size.method(validity_checks[option])[option_value]
-                record.errors.add(attr, key, :default => custom_message, :count => option_value) 
-              end
-            end
-        end
-      end
-
-      alias_method :validates_size_of, :validates_length_of
-
-
-      # Validates whether the value of the specified attributes are unique across the system. Useful for making sure that only one user
-      # can be named "davidhh".
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_uniqueness_of :user_name, :scope => :account_id
-      #   end
-      #
-      # It can also validate whether the value of the specified attributes are unique based on multiple scope parameters.  For example,
-      # making sure that a teacher can only be on the schedule once per semester for a particular class.
-      #
-      #   class TeacherSchedule < ActiveRecord::Base
-      #     validates_uniqueness_of :teacher_id, :scope => [:semester_id, :class_id]
-      #   end
-      #
-      # When the record is created, a check is performed to make sure that no record exists in the database with the given value for the specified
-      # attribute (that maps to a column). When the record is updated, the same check is made but disregarding the record itself.
-      #
-      # Configuration options:
-      # * <tt>:message</tt> - Specifies a custom error message (default is: "has already been taken").
-      # * <tt>:scope</tt> - One or more columns by which to limit the scope of the uniqueness constraint.
-      # * <tt>:case_sensitive</tt> - Looks for an exact match. Ignored by non-text columns (+true+ by default).
-      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
-      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      #
-      # === Concurrency and integrity
-      #
-      # Using this validation method in conjunction with ActiveRecord::Base#save
-      # does not guarantee the absence of duplicate record insertions, because
-      # uniqueness checks on the application level are inherently prone to race
-      # conditions. For example, suppose that two users try to post a Comment at
-      # the same time, and a Comment's title must be unique. At the database-level,
-      # the actions performed by these users could be interleaved in the following manner:
-      #
-      #               User 1                 |               User 2
-      #  ------------------------------------+--------------------------------------
-      #  # User 1 checks whether there's     |
-      #  # already a comment with the title  |
-      #  # 'My Post'. This is not the case.  |
-      #  SELECT * FROM comments              |
-      #  WHERE title = 'My Post'             |
-      #                                      |
-      #                                      | # User 2 does the same thing and also
-      #                                      | # infers that his title is unique.
-      #                                      | SELECT * FROM comments
-      #                                      | WHERE title = 'My Post'
-      #                                      |
-      #  # User 1 inserts his comment.       |
-      #  INSERT INTO comments                |
-      #  (title, content) VALUES             |
-      #  ('My Post', 'hi!')                  |
-      #                                      |
-      #                                      | # User 2 does the same thing.
-      #                                      | INSERT INTO comments
-      #                                      | (title, content) VALUES
-      #                                      | ('My Post', 'hello!')
-      #                                      |
-      #                                      | # ^^^^^^
-      #                                      | # Boom! We now have a duplicate
-      #                                      | # title!
-      #
-      # This could even happen if you use transactions with the 'serializable'
-      # isolation level. There are several ways to get around this problem:
-      # - By locking the database table before validating, and unlocking it after
-      #   saving. However, table locking is very expensive, and thus not
-      #   recommended.
-      # - By locking a lock file before validating, and unlocking it after saving.
-      #   This does not work if you've scaled your Rails application across
-      #   multiple web servers (because they cannot share lock files, or cannot
-      #   do that efficiently), and thus not recommended.
-      # - Creating a unique index on the field, by using
-      #   ActiveRecord::ConnectionAdapters::SchemaStatements#add_index. In the
-      #   rare case that a race condition occurs, the database will guarantee
-      #   the field's uniqueness.
-      #   
-      #   When the database catches such a duplicate insertion,
-      #   ActiveRecord::Base#save will raise an ActiveRecord::StatementInvalid
-      #   exception. You can either choose to let this error propagate (which
-      #   will result in the default Rails exception page being shown), or you
-      #   can catch it and restart the transaction (e.g. by telling the user
-      #   that the title already exists, and asking him to re-enter the title).
-      #   This technique is also known as optimistic concurrency control:
-      #   http://en.wikipedia.org/wiki/Optimistic_concurrency_control
-      #   
-      #   Active Record currently provides no way to distinguish unique
-      #   index constraint errors from other types of database errors, so you
-      #   will have to parse the (database-specific) exception message to detect
-      #   such a case.
-      def validates_uniqueness_of(*attr_names)
-        configuration = { :case_sensitive => true }
-        configuration.update(attr_names.extract_options!)
-
-        validates_each(attr_names,configuration) do |record, attr_name, value|
-          # The check for an existing value should be run from a class that
-          # isn't abstract. This means working down from the current class
-          # (self), to the first non-abstract class. Since classes don't know
-          # their subclasses, we have to build the hierarchy between self and
-          # the record's class.
-          class_hierarchy = [record.class]
-          while class_hierarchy.first != self
-            class_hierarchy.insert(0, class_hierarchy.first.superclass)
-          end
-
-          # Now we can work our way down the tree to the first non-abstract
-          # class (which has a database table to query from).
-          finder_class = class_hierarchy.detect { |klass| !klass.abstract_class? }
-
-          column = finder_class.columns_hash[attr_name.to_s]
-
-          if value.nil?
-            comparison_operator = "IS ?"
-          elsif column.text?
-            comparison_operator = "#{connection.case_sensitive_equality_operator} ?"
-            value = column.limit ? value.to_s[0, column.limit] : value.to_s
-          else
-            comparison_operator = "= ?"
-          end
-
-          sql_attribute = "#{record.class.quoted_table_name}.#{connection.quote_column_name(attr_name)}"
-
-          if value.nil? || (configuration[:case_sensitive] || !column.text?)
-            condition_sql = "#{sql_attribute} #{comparison_operator}"
-            condition_params = [value]
-          else
-            condition_sql = "LOWER(#{sql_attribute}) #{comparison_operator}"
-            condition_params = [value.mb_chars.downcase]
-          end
-
-          if scope = configuration[:scope]
-            Array(scope).map do |scope_item|
-              scope_value = record.send(scope_item)
-              condition_sql << " AND " << attribute_condition("#{record.class.quoted_table_name}.#{scope_item}", scope_value)
-              condition_params << scope_value
-            end
-          end
-
-          unless record.new_record?
-            condition_sql << " AND #{record.class.quoted_table_name}.#{record.class.primary_key} <> ?"
-            condition_params << record.send(:id)
-          end
-
-          finder_class.with_exclusive_scope do
-            if finder_class.exists?([condition_sql, *condition_params])
-              record.errors.add(attr_name, :taken, :default => configuration[:message], :value => value)
-            end
-          end
-        end
-      end
-
-
-      # Validates whether the value of the specified attribute is of the correct form by matching it against the regular expression
-      # provided.
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i, :on => :create
-      #   end
-      #
-      # Note: use <tt>\A</tt> and <tt>\Z</tt> to match the start and end of the string, <tt>^</tt> and <tt>$</tt> match the start/end of a line.
-      #
-      # A regular expression must be provided or else an exception will be raised.
-      #
-      # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "is invalid").
-      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
-      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
-      # * <tt>:with</tt> - The regular expression used to validate the format with (note: must be supplied!).
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      def validates_format_of(*attr_names)
-        configuration = { :on => :save, :with => nil }
-        configuration.update(attr_names.extract_options!)
-
-        raise(ArgumentError, "A regular expression must be supplied as the :with option of the configuration hash") unless configuration[:with].is_a?(Regexp)
-
-        validates_each(attr_names, configuration) do |record, attr_name, value|
-          unless value.to_s =~ configuration[:with]
-            record.errors.add(attr_name, :invalid, :default => configuration[:message], :value => value) 
-          end
-        end
-      end
-
-      # Validates whether the value of the specified attribute is available in a particular enumerable object.
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_inclusion_of :gender, :in => %w( m f )
-      #     validates_inclusion_of :age, :in => 0..99
-      #     validates_inclusion_of :format, :in => %w( jpg gif png ), :message => "extension {{value}} is not included in the list"
-      #   end
-      #
-      # Configuration options:
-      # * <tt>:in</tt> - An enumerable object of available items.
-      # * <tt>:message</tt> - Specifies a custom error message (default is: "is not included in the list").
-      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
-      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      def validates_inclusion_of(*attr_names)
-        configuration = { :on => :save }
-        configuration.update(attr_names.extract_options!)
-
-        enum = configuration[:in] || configuration[:within]
-
-        raise(ArgumentError, "An object with the method include? is required must be supplied as the :in option of the configuration hash") unless enum.respond_to?(:include?)
-
-        validates_each(attr_names, configuration) do |record, attr_name, value|
-          unless enum.include?(value)
-            record.errors.add(attr_name, :inclusion, :default => configuration[:message], :value => value) 
-          end
-        end
-      end
-
-      # Validates that the value of the specified attribute is not in a particular enumerable object.
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_exclusion_of :username, :in => %w( admin superuser ), :message => "You don't belong here"
-      #     validates_exclusion_of :age, :in => 30..60, :message => "This site is only for under 30 and over 60"
-      #     validates_exclusion_of :format, :in => %w( mov avi ), :message => "extension {{value}} is not allowed"
-      #   end
-      #
-      # Configuration options:
-      # * <tt>:in</tt> - An enumerable object of items that the value shouldn't be part of.
-      # * <tt>:message</tt> - Specifies a custom error message (default is: "is reserved").
-      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
-      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      def validates_exclusion_of(*attr_names)
-        configuration = { :on => :save }
-        configuration.update(attr_names.extract_options!)
-
-        enum = configuration[:in] || configuration[:within]
-
-        raise(ArgumentError, "An object with the method include? is required must be supplied as the :in option of the configuration hash") unless enum.respond_to?(:include?)
-
-        validates_each(attr_names, configuration) do |record, attr_name, value|
-          if enum.include?(value)
-            record.errors.add(attr_name, :exclusion, :default => configuration[:message], :value => value) 
-          end
-        end
-      end
-
-      # Validates whether the associated object or objects are all valid themselves. Works with any kind of association.
-      #
-      #   class Book < ActiveRecord::Base
-      #     has_many :pages
-      #     belongs_to :library
-      #
-      #     validates_associated :pages, :library
-      #   end
-      #
-      # Warning: If, after the above definition, you then wrote:
-      #
-      #   class Page < ActiveRecord::Base
-      #     belongs_to :book
-      #
-      #     validates_associated :book
-      #   end
-      #
-      # this would specify a circular dependency and cause infinite recursion.
-      #
-      # NOTE: This validation will not fail if the association hasn't been assigned. If you want to ensure that the association
-      # is both present and guaranteed to be valid, you also need to use +validates_presence_of+.
-      #
-      # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "is invalid")
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      def validates_associated(*attr_names)
-        configuration = { :on => :save }
-        configuration.update(attr_names.extract_options!)
-
-        validates_each(attr_names, configuration) do |record, attr_name, value|
-          unless (value.is_a?(Array) ? value : [value]).collect { |r| r.nil? || r.valid? }.all?
-            record.errors.add(attr_name, :invalid, :default => configuration[:message], :value => value)
-          end
-        end
-      end
-
-      # Validates whether the value of the specified attribute is numeric by trying to convert it to
-      # a float with Kernel.Float (if <tt>only_integer</tt> is false) or applying it to the regular expression
-      # <tt>/\A[\+\-]?\d+\Z/</tt> (if <tt>only_integer</tt> is set to true).
-      #
-      #   class Person < ActiveRecord::Base
-      #     validates_numericality_of :value, :on => :create
-      #   end
-      #
-      # Configuration options:
-      # * <tt>:message</tt> - A custom error message (default is: "is not a number").
-      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
-      # * <tt>:only_integer</tt> - Specifies whether the value has to be an integer, e.g. an integral value (default is +false+).
-      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+ (default is +false+). Notice that for fixnum and float columns empty strings are converted to +nil+.
-      # * <tt>:greater_than</tt> - Specifies the value must be greater than the supplied value.
-      # * <tt>:greater_than_or_equal_to</tt> - Specifies the value must be greater than or equal the supplied value.
-      # * <tt>:equal_to</tt> - Specifies the value must be equal to the supplied value.
-      # * <tt>:less_than</tt> - Specifies the value must be less than the supplied value.
-      # * <tt>:less_than_or_equal_to</tt> - Specifies the value must be less than or equal the supplied value.
-      # * <tt>:odd</tt> - Specifies the value must be an odd number.
-      # * <tt>:even</tt> - Specifies the value must be an even number.
-      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
-      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
-      #   method, proc or string should return or evaluate to a true or false value.
-      def validates_numericality_of(*attr_names)
-        configuration = { :on => :save, :only_integer => false, :allow_nil => false }
-        configuration.update(attr_names.extract_options!)
-
-
-        numericality_options = ALL_NUMERICALITY_CHECKS.keys & configuration.keys
-
-        (numericality_options - [ :odd, :even ]).each do |option|
-          raise ArgumentError, ":#{option} must be a number" unless configuration[option].is_a?(Numeric)
-        end
-
-        validates_each(attr_names,configuration) do |record, attr_name, value|
-          raw_value = record.send("#{attr_name}_before_type_cast") || value
-
-          next if configuration[:allow_nil] and raw_value.nil?
-
-          if configuration[:only_integer]
-            unless raw_value.to_s =~ /\A[+-]?\d+\Z/
-              record.errors.add(attr_name, :not_a_number, :value => raw_value, :default => configuration[:message])
-              next
-            end
-            raw_value = raw_value.to_i
-          else
-            begin
-              raw_value = Kernel.Float(raw_value)
-            rescue ArgumentError, TypeError
-              record.errors.add(attr_name, :not_a_number, :value => raw_value, :default => configuration[:message])
-              next
-            end
-          end
-
-          numericality_options.each do |option|
-            case option
-              when :odd, :even
-                unless raw_value.to_i.method(ALL_NUMERICALITY_CHECKS[option])[]
-                  record.errors.add(attr_name, option, :value => raw_value, :default => configuration[:message]) 
-                end
-              else
-                record.errors.add(attr_name, option, :default => configuration[:message], :value => raw_value, :count => configuration[option]) unless raw_value.method(ALL_NUMERICALITY_CHECKS[option])[configuration[option]]
-            end
-          end
-        end
-      end
-
       # Creates an object just like Base.create but calls save! instead of save
       # so an exception is raised if the record is invalid.
       def create!(attributes = nil, &block)
@@ -991,17 +37,8 @@ module ActiveRecord
           object
         end
       end
-
-      private
-        def validation_method(on)
-          case on
-            when :save   then :validate
-            when :create then :validate_on_create
-            when :update then :validate_on_update
-          end
-        end
     end
-
+    
     # The validation process on save can be skipped by passing false. The regular Base#save method is
     # replaced with this when the validations module is mixed in, which it is by default.
     def save_with_validation(perform_validation = true)
@@ -1022,45 +59,9 @@ module ActiveRecord
       end
     end
 
-    # Runs +validate+ and +validate_on_create+ or +validate_on_update+ and returns true if no errors were added otherwise false.
-    def valid?
-      errors.clear
-
-      run_callbacks(:validate)
-      validate
-
-      if new_record?
-        run_callbacks(:validate_on_create)
-        validate_on_create
-      else
-        run_callbacks(:validate_on_update)
-        validate_on_update
-      end
-
-      errors.empty?
-    end
-
-    # Performs the opposite of <tt>valid?</tt>. Returns true if errors were added, false otherwise.
-    def invalid?
-      !valid?
-    end
-
     # Returns the Errors object that holds all information about attribute error messages.
     def errors
       @errors ||= Errors.new(self)
     end
-
-    protected
-      # Overwrite this method for validation checks on all saves and use <tt>Errors.add(field, msg)</tt> for invalid attributes.
-      def validate
-      end
-
-      # Overwrite this method for validation checks used only on creation.
-      def validate_on_create
-      end
-
-      # Overwrite this method for validation checks used only on updates.
-      def validate_on_update
-      end
   end
 end
diff --git a/activerecord/test/cases/autosave_association_test.rb b/activerecord/test/cases/autosave_association_test.rb
index 436f50d395..4018036a9f 100644
--- a/activerecord/test/cases/autosave_association_test.rb
+++ b/activerecord/test/cases/autosave_association_test.rb
@@ -713,8 +713,8 @@ class TestAutosaveAssociationOnABelongsToAssociation < ActiveRecord::TestCase
 
   def test_should_automatically_validate_the_associated_model
     @ship.pirate.catchphrase = ''
-    assert !@ship.valid?
-    assert !@ship.errors.on(:pirate_catchphrase).blank?
+    assert @ship.invalid?
+    assert @ship.errors[:pirate_catchphrase].any?
   end
 
   def test_should_merge_errors_on_the_associated_model_onto_the_parent_even_if_it_is_not_valid
diff --git a/activerecord/test/cases/validations_i18n_test.rb b/activerecord/test/cases/validations_i18n_test.rb
index 66982346e9..5edb3d3239 100644
--- a/activerecord/test/cases/validations_i18n_test.rb
+++ b/activerecord/test/cases/validations_i18n_test.rb
@@ -39,8 +39,8 @@ class ActiveRecordValidationsI18nTests < ActiveSupport::TestCase
   end
 
   def test_default_error_messages_is_deprecated
-    assert_deprecated('ActiveRecord::Errors.default_error_messages') do
-      ActiveRecord::Errors.default_error_messages
+    assert_deprecated('Errors.default_error_messages') do
+      ActiveModel::Errors.default_error_messages
     end
   end
 
@@ -70,7 +70,7 @@ class ActiveRecordValidationsI18nTests < ActiveSupport::TestCase
     end
   end
 
-  # ActiveRecord::Errors
+  # ActiveModel::Errors
   def test_errors_generate_message_translates_custom_model_attribute_key
 
     I18n.expects(:translate).with(
@@ -161,7 +161,7 @@ class ActiveRecordValidationsI18nTests < ActiveSupport::TestCase
   end
 
   def test_errors_full_messages_translates_human_attribute_name_for_model_attributes
-    @topic.errors.instance_variable_set :@errors, { 'title' => ['empty'] }
+    @topic.errors.add('title', 'empty')
     I18n.expects(:translate).with(:"topic.title", :default => ['Title'], :scope => [:activerecord, :attributes], :count => 1).returns('Title')
     @topic.errors.full_messages :locale => 'en'
   end
diff --git a/activerecord/test/cases/validations_test.rb b/activerecord/test/cases/validations_test.rb
index c20f5ae63e..bef8e15b30 100644
--- a/activerecord/test/cases/validations_test.rb
+++ b/activerecord/test/cases/validations_test.rb
@@ -75,7 +75,7 @@ class ValidationsTest < ActiveRecord::TestCase
     r.title = "There's no content!"
     assert !r.valid?
     assert r.errors.invalid?("content"), "A reply without content should mark that attribute as invalid"
-    assert_equal "Empty", r.errors.on("content"), "A reply without content should contain an error"
+    assert_equal ["Empty"], r.errors["content"], "A reply without content should contain an error"
     assert_equal 1, r.errors.count
   end
 
@@ -84,10 +84,10 @@ class ValidationsTest < ActiveRecord::TestCase
     assert !r.valid?
 
     assert r.errors.invalid?("title"), "A reply without title should mark that attribute as invalid"
-    assert_equal "Empty", r.errors.on("title"), "A reply without title should contain an error"
+    assert_equal ["Empty"], r.errors["title"], "A reply without title should contain an error"
 
     assert r.errors.invalid?("content"), "A reply without content should mark that attribute as invalid"
-    assert_equal "Empty", r.errors.on("content"), "A reply without content should contain an error"
+    assert_equal ["Empty"], r.errors["content"], "A reply without content should contain an error"
 
     assert_equal 2, r.errors.count
   end
@@ -97,7 +97,7 @@ class ValidationsTest < ActiveRecord::TestCase
     r.title = "Wrong Create"
     assert !r.valid?
     assert r.errors.invalid?("title"), "A reply with a bad title should mark that attribute as invalid"
-    assert_equal "is Wrong Create", r.errors.on("title"), "A reply with a bad content should contain an error"
+    assert_equal "is Wrong Create", r.errors.on(:title), "A reply with a bad content should contain an error"
   end
 
   def test_error_on_update
@@ -110,7 +110,7 @@ class ValidationsTest < ActiveRecord::TestCase
     assert !r.save, "Second save should fail"
 
     assert r.errors.invalid?("title"), "A reply with a bad title should mark that attribute as invalid"
-    assert_equal "is Wrong Update", r.errors.on("title"), "A reply with a bad content should contain an error"
+    assert_equal "is Wrong Update", r.errors.on(:title), "A reply with a bad content should contain an error"
   end
 
   def test_invalid_record_exception
@@ -177,7 +177,7 @@ class ValidationsTest < ActiveRecord::TestCase
     r.save
 
     errors = []
-    r.errors.each { |attr, msg| errors << [attr, msg] }
+    r.errors.each {|attr, messages| errors << [attr.to_s, messages] }
 
     assert errors.include?(["title", "Empty"])
     assert errors.include?(["content", "Empty"])
@@ -189,8 +189,7 @@ class ValidationsTest < ActiveRecord::TestCase
     r.content = "Mismatch"
     r.save
 
-    errors = []
-    r.errors.each_full { |error| errors << error }
+    errors = r.errors.to_a
 
     assert_equal "Title is Wrong Create", errors[0]
     assert_equal "Title is Content Mismatch", errors[1]
@@ -234,8 +233,8 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.new("title" => "valid", "content" => "whatever")
     assert !t.save
     assert_equal 4, hits
-    assert_equal %w(gotcha gotcha), t.errors.on(:title)
-    assert_equal %w(gotcha gotcha), t.errors.on(:content)
+    assert_equal %w(gotcha gotcha), t.errors[:title]
+    assert_equal %w(gotcha gotcha), t.errors[:content]
   end
 
   def test_no_title_confirmation
@@ -277,7 +276,7 @@ class ValidationsTest < ActiveRecord::TestCase
 
     t = Topic.create("title" => "We should be confirmed","terms_of_service" => "")
     assert !t.save
-    assert_equal "must be accepted", t.errors.on(:terms_of_service)
+    assert_equal ["must be accepted"], t.errors[:terms_of_service]
 
     t.terms_of_service = "1"
     assert t.save
@@ -289,7 +288,7 @@ class ValidationsTest < ActiveRecord::TestCase
 
     t = Topic.create("title" => "We should be confirmed","eula" => "")
     assert !t.save
-    assert_equal "must be abided", t.errors.on(:eula)
+    assert_equal ["must be abided"], t.errors[:eula]
 
     t.eula = "1"
     assert t.save
@@ -300,7 +299,7 @@ class ValidationsTest < ActiveRecord::TestCase
 
     t = Topic.create("title" => "We should be confirmed", "terms_of_service" => "")
     assert !t.save
-    assert_equal "must be accepted", t.errors.on(:terms_of_service)
+    assert_equal ["must be accepted"], t.errors[:terms_of_service]
 
     t.terms_of_service = "I agree."
     assert t.save
@@ -328,14 +327,14 @@ class ValidationsTest < ActiveRecord::TestCase
 
     t = Topic.create
     assert !t.save
-    assert_equal "can't be blank", t.errors.on(:title)
-    assert_equal "can't be blank", t.errors.on(:content)
+    assert_equal ["can't be blank"], t.errors[:title]
+    assert_equal ["can't be blank"], t.errors[:content]
 
     t.title = "something"
     t.content  = "   "
 
     assert !t.save
-    assert_equal "can't be blank", t.errors.on(:content)
+    assert_equal ["can't be blank"], t.errors[:content]
 
     t.content = "like stuff"
 
@@ -354,7 +353,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t2 = Topic.new("title" => "I'm unique!")
     assert !t2.valid?, "Shouldn't be valid"
     assert !t2.save, "Shouldn't save t2 as unique"
-    assert_equal "has already been taken", t2.errors.on(:title)
+    assert_equal ["has already been taken"], t2.errors[:title]
 
     t2.title = "Now Im really also unique"
     assert t2.save, "Should now save t2 as unique"
@@ -441,15 +440,15 @@ class ValidationsTest < ActiveRecord::TestCase
     t2 = Topic.new("title" => "I'm UNIQUE!", :parent_id => 1)
     assert !t2.valid?, "Shouldn't be valid"
     assert !t2.save, "Shouldn't save t2 as unique"
-    assert t2.errors.on(:title)
-    assert t2.errors.on(:parent_id)
-    assert_equal "has already been taken", t2.errors.on(:title)
+    assert t2.errors[:title].any?
+    assert t2.errors[:parent_id].any?
+    assert_equal ["has already been taken"], t2.errors[:title]
 
     t2.title = "I'm truly UNIQUE!"
     assert !t2.valid?, "Shouldn't be valid"
     assert !t2.save, "Shouldn't save t2 as unique"
-    assert_nil t2.errors.on(:title)
-    assert t2.errors.on(:parent_id)
+    assert t2.errors[:title].empty?
+    assert t2.errors[:parent_id].any?
 
     t2.parent_id = 4
     assert t2.save, "Should now save t2 as unique"
@@ -484,16 +483,16 @@ class ValidationsTest < ActiveRecord::TestCase
     t2 = Topic.new("title" => "I'M UNIQUE!")
     assert t2.valid?, "Should be valid"
     assert t2.save, "Should save t2 as unique"
-    assert !t2.errors.on(:title)
-    assert !t2.errors.on(:parent_id)
-    assert_not_equal "has already been taken", t2.errors.on(:title)
+    assert t2.errors[:title].empty?
+    assert t2.errors[:parent_id].empty?
+    assert_not_equal ["has already been taken"], t2.errors[:title]
 
     t3 = Topic.new("title" => "I'M uNiQUe!")
     assert t3.valid?, "Should be valid"
     assert t3.save, "Should save t2 as unique"
-    assert !t3.errors.on(:title)
-    assert !t3.errors.on(:parent_id)
-    assert_not_equal "has already been taken", t3.errors.on(:title)
+    assert t3.errors[:title].empty?
+    assert t3.errors[:parent_id].empty?
+    assert_not_equal ["has already been taken"], t3.errors[:title]
   end
 
   def test_validate_case_sensitive_uniqueness_with_attribute_passed_as_integer
@@ -502,13 +501,13 @@ class ValidationsTest < ActiveRecord::TestCase
 
     t2 = Topic.new('title' => 101)
     assert !t2.valid?
-    assert t2.errors.on(:title)
+    assert t2.errors[:title]
   end
 
   def test_validate_uniqueness_with_non_standard_table_names
     i1 = WarehouseThing.create(:value => 1000)
     assert !i1.valid?, "i1 should not be valid"
-    assert i1.errors.on(:value), "Should not be empty"
+    assert i1.errors[:value].any?, "Should not be empty"
   end
 
   def test_validates_uniqueness_inside_with_scope
@@ -546,26 +545,26 @@ class ValidationsTest < ActiveRecord::TestCase
     # Should use validation from base class (which is abstract)
     w2 = IneptWizard.new(:name => "Rincewind", :city => "Quirm")
     assert !w2.valid?, "w2 shouldn't be valid"
-    assert w2.errors.on(:name), "Should have errors for name"
-    assert_equal "has already been taken", w2.errors.on(:name), "Should have uniqueness message for name"
+    assert w2.errors[:name].any?, "Should have errors for name"
+    assert_equal ["has already been taken"], w2.errors[:name], "Should have uniqueness message for name"
 
     w3 = Conjurer.new(:name => "Rincewind", :city => "Quirm")
     assert !w3.valid?, "w3 shouldn't be valid"
-    assert w3.errors.on(:name), "Should have errors for name"
-    assert_equal "has already been taken", w3.errors.on(:name), "Should have uniqueness message for name"
+    assert w3.errors[:name].any?, "Should have errors for name"
+    assert_equal ["has already been taken"], w3.errors[:name], "Should have uniqueness message for name"
 
     w4 = Conjurer.create(:name => "The Amazing Bonko", :city => "Quirm")
     assert w4.valid?, "Saving w4"
 
     w5 = Thaumaturgist.new(:name => "The Amazing Bonko", :city => "Lancre")
     assert !w5.valid?, "w5 shouldn't be valid"
-    assert w5.errors.on(:name), "Should have errors for name"
-    assert_equal "has already been taken", w5.errors.on(:name), "Should have uniqueness message for name"
+    assert w5.errors[:name].any?, "Should have errors for name"
+    assert_equal ["has already been taken"], w5.errors[:name], "Should have uniqueness message for name"
 
     w6 = Thaumaturgist.new(:name => "Mustrum Ridcully", :city => "Quirm")
     assert !w6.valid?, "w6 shouldn't be valid"
-    assert w6.errors.on(:city), "Should have errors for city"
-    assert_equal "has already been taken", w6.errors.on(:city), "Should have uniqueness message for city"
+    assert w6.errors[:city].any?, "Should have errors for city"
+    assert_equal ["has already been taken"], w6.errors[:city], "Should have uniqueness message for city"
   end
 
   def test_validate_format
@@ -574,13 +573,13 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "i'm incorrect", "content" => "Validation macros rule!")
     assert !t.valid?, "Shouldn't be valid"
     assert !t.save, "Shouldn't save because it's invalid"
-    assert_equal "is bad data", t.errors.on(:title)
-    assert_nil t.errors.on(:content)
+    assert_equal ["is bad data"], t.errors[:title]
+    assert t.errors[:content].empty?
 
     t.title = "Validation macros rule!"
 
     assert t.save
-    assert_nil t.errors.on(:title)
+    assert t.errors[:title].empty?
 
     assert_raise(ArgumentError) { Topic.validates_format_of(:title, :content) }
   end
@@ -600,8 +599,8 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "72x", "content" => "6789")
     assert !t.valid?, "Shouldn't be valid"
     assert !t.save, "Shouldn't save because it's invalid"
-    assert_equal "is bad data", t.errors.on(:title)
-    assert_nil t.errors.on(:content)
+    assert_equal ["is bad data"], t.errors[:title]
+    assert t.errors[:content].empty?
 
     t.title = "-11"
     assert !t.valid?, "Shouldn't be valid"
@@ -618,7 +617,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t.title = "1"
 
     assert t.save
-    assert_nil t.errors.on(:title)
+    assert t.errors[:title].empty?
   end
 
   def test_validate_format_with_formatted_message
@@ -639,7 +638,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t.title = "uhoh"
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "is not included in the list", t.errors["title"]
+    assert_equal "is not included in the list", t.errors.on(:title)
 
     assert_raise(ArgumentError) { Topic.validates_inclusion_of( :title, :in => nil ) }
     assert_raise(ArgumentError) { Topic.validates_inclusion_of( :title, :in => 0) }
@@ -692,7 +691,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "uhoh", "content" => "abc")
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "option uhoh is not in the list", t.errors["title"]
+    assert_equal "option uhoh is not in the list", t.errors.on(:title)
   end
 
   def test_numericality_with_allow_nil_and_getter_method
@@ -719,7 +718,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "monkey")
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "option monkey is restricted", t.errors["title"]
+    assert_equal "option monkey is restricted", t.errors.on(:title)
   end
 
   def test_validates_length_of_using_minimum
@@ -731,17 +730,17 @@ class ValidationsTest < ActiveRecord::TestCase
     t.title = "not"
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "is too short (minimum is 5 characters)", t.errors["title"]
+    assert_equal "is too short (minimum is 5 characters)", t.errors.on(:title)
 
     t.title = ""
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "is too short (minimum is 5 characters)", t.errors["title"]
+    assert_equal "is too short (minimum is 5 characters)", t.errors.on(:title)
 
     t.title = nil
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "is too short (minimum is 5 characters)", t.errors["title"]
+    assert_equal ["is too short (minimum is 5 characters)"], t.errors["title"]
   end
 
   def test_optionally_validates_length_of_using_minimum
@@ -763,7 +762,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t.title = "notvalid"
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "is too long (maximum is 5 characters)", t.errors["title"]
+    assert_equal "is too long (maximum is 5 characters)", t.errors.on(:title)
 
     t.title = ""
     assert t.valid?
@@ -817,7 +816,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "thisisnotvalid", "content" => "whatever")
     assert !t.save
     assert t.errors.on(:title)
-    assert_equal "my string is too long: 10", t.errors[:title]
+    assert_equal "my string is too long: 10", t.errors.on(:title)
 
     t.title = "butthisis"
     assert t.save
@@ -842,7 +841,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t.title = "not"
     assert !t.save
     assert t.errors.on(:title)
-    assert_equal "my string is too short: 5", t.errors[:title]
+    assert_equal "my string is too short: 5", t.errors.on(:title)
 
     t.title = "valid"
     t.content = "andthisistoolong"
@@ -862,7 +861,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t.title = "notvalid"
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "is the wrong length (should be 5 characters)", t.errors["title"]
+    assert_equal "is the wrong length (should be 5 characters)", t.errors.on(:title)
 
     t.title = ""
     assert !t.valid?
@@ -896,13 +895,13 @@ class ValidationsTest < ActiveRecord::TestCase
 
   def test_validates_length_with_globally_modified_error_message
     ActiveSupport::Deprecation.silence do
-      ActiveRecord::Errors.default_error_messages[:too_short] = 'tu est trops petit hombre {{count}}'
+      ActiveModel::Errors.default_error_messages[:too_short] = 'tu est trops petit hombre {{count}}'
     end
     Topic.validates_length_of :title, :minimum => 10
     t = Topic.create(:title => 'too short')
     assert !t.valid?
 
-    assert_equal 'tu est trops petit hombre 10', t.errors['title']
+    assert_equal 'tu est trops petit hombre 10', t.errors.on(:title)
   end
 
   def test_validates_size_of_association
@@ -948,7 +947,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "uhoh", "content" => "whatever")
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "boo 5", t.errors["title"]
+    assert_equal "boo 5", t.errors.on(:title)
   end
 
   def test_validates_length_of_custom_errors_for_minimum_with_too_short
@@ -956,7 +955,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "uhoh", "content" => "whatever")
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert_equal "hoo 5", t.errors.on(:title)
   end
 
   def test_validates_length_of_custom_errors_for_maximum_with_message
@@ -964,44 +963,44 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
     assert t.errors.on(:title)
-    assert_equal "boo 5", t.errors["title"]
+    assert_equal ["boo 5"], t.errors[:title]
   end
 
   def test_validates_length_of_custom_errors_for_in
     Topic.validates_length_of(:title, :in => 10..20, :message => "hoo {{count}}")
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 10", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 10"], t.errors["title"]
 
     t = Topic.create("title" => "uhohuhohuhohuhohuhohuhohuhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 20", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 20"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_maximum_with_too_long
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}" )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_is_with_message
     Topic.validates_length_of( :title, :is=>5, :message=>"boo {{count}}" )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "boo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["boo 5"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_is_with_wrong_length
     Topic.validates_length_of( :title, :is=>5, :wrong_length=>"hoo {{count}}" )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_validates_length_of_using_minimum_utf8
@@ -1013,8 +1012,8 @@ class ValidationsTest < ActiveRecord::TestCase
 
       t.title = "一二三四"
       assert !t.valid?
-      assert t.errors.on(:title)
-      assert_equal "is too short (minimum is 5 characters)", t.errors["title"]
+      assert t.errors[:title].any?
+      assert_equal ["is too short (minimum is 5 characters)"], t.errors["title"]
     end
   end
 
@@ -1027,8 +1026,8 @@ class ValidationsTest < ActiveRecord::TestCase
 
       t.title = "一二34五六"
       assert !t.valid?
-      assert t.errors.on(:title)
-      assert_equal "is too long (maximum is 5 characters)", t.errors["title"]
+      assert t.errors[:title].any?
+      assert_equal ["is too long (maximum is 5 characters)"], t.errors["title"]
     end
   end
 
@@ -1038,8 +1037,8 @@ class ValidationsTest < ActiveRecord::TestCase
 
       t = Topic.new("title" => "一二", "content" => "12三四五六七")
       assert !t.valid?
-      assert_equal "is too short (minimum is 3 characters)", t.errors.on(:title)
-      assert_equal "is too long (maximum is 5 characters)", t.errors.on(:content)
+      assert_equal ["is too short (minimum is 3 characters)"], t.errors[:title]
+      assert_equal ["is too long (maximum is 5 characters)"], t.errors[:content]
       t.title = "一二三"
       t.content  = "12三"
       assert t.valid?
@@ -1067,8 +1066,8 @@ class ValidationsTest < ActiveRecord::TestCase
 
       t = Topic.create("title" => "一二三四五六七八九十A", "content" => "whatever")
       assert !t.save
-      assert t.errors.on(:title)
-      assert_equal "長すぎます: 10", t.errors[:title]
+      assert t.errors[:title].any?
+      assert_equal "長すぎます: 10", t.errors[:title].first
 
       t.title = "一二三四五六七八九"
       assert t.save
@@ -1090,16 +1089,16 @@ class ValidationsTest < ActiveRecord::TestCase
 
       t = Topic.create("title" => "一二三4", "content" => "whatever")
       assert !t.save
-      assert t.errors.on(:title)
+      assert t.errors[:title].any?
 
       t.title = "1二三4"
       assert !t.save
-      assert t.errors.on(:title)
-      assert_equal "短すぎます: 5", t.errors[:title]
+      assert t.errors[:title].any?
+      assert_equal "短すぎます: 5", t.errors.on(:title)
 
       t.title = "一二三四五六七八九十A"
       assert !t.save
-      assert t.errors.on(:title)
+      assert t.errors[:title].any?
 
       t.title = "一二345"
       assert t.save
@@ -1115,8 +1114,8 @@ class ValidationsTest < ActiveRecord::TestCase
 
       t.title = "一二345六"
       assert !t.valid?
-      assert t.errors.on(:title)
-      assert_equal "is the wrong length (should be 5 characters)", t.errors["title"]
+      assert t.errors[:title].any?
+      assert_equal ["is the wrong length (should be 5 characters)"], t.errors["title"]
     end
   end
 
@@ -1128,8 +1127,8 @@ class ValidationsTest < ActiveRecord::TestCase
 
     t.content = "not long enough"
     assert !t.valid?
-    assert t.errors.on(:content)
-    assert_equal "Your essay must be at least 5 words.", t.errors[:content]
+    assert t.errors[:content].any?
+    assert_equal ["Your essay must be at least 5 words."], t.errors[:content]
   end
 
   def test_validates_size_of_association_utf8
@@ -1138,7 +1137,7 @@ class ValidationsTest < ActiveRecord::TestCase
         assert_nothing_raised { Owner.validates_size_of :pets, :minimum => 1 }
         o = Owner.new('name' => 'あいうえおかきくけこ')
         assert !o.save
-        assert o.errors.on(:pets)
+        assert o.errors[:pets].any?
         o.pets.build('name' => 'あいうえおかきくけこ')
         assert o.valid?
       end
@@ -1150,7 +1149,7 @@ class ValidationsTest < ActiveRecord::TestCase
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     t.replies << [r = Reply.new("title" => "A reply"), r2 = Reply.new("title" => "Another reply", "content" => "non-empty"), r3 = Reply.new("title" => "Yet another reply"), r4 = Reply.new("title" => "The last reply", "content" => "non-empty")]
     assert !t.valid?
-    assert t.errors.on(:replies)
+    assert t.errors[:replies].any?
     assert_equal 1, r.errors.count  # make sure all associated objects have been validated
     assert_equal 0, r2.errors.count
     assert_equal 1, r3.errors.count
@@ -1166,7 +1165,7 @@ class ValidationsTest < ActiveRecord::TestCase
       r = Reply.new("title" => "A reply", "content" => "with content!")
       r.topic = Topic.create("title" => "uhohuhoh")
       assert !r.valid?
-      assert r.errors.on(:topic)
+      assert r.errors[:topic].any?
       r.topic.content = "non-empty"
       assert r.valid?
     end
@@ -1176,8 +1175,8 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validate { |topic| topic.errors.add("title", "will never be valid") }
     t = Topic.create("title" => "Title", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "will never be valid", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["will never be valid"], t.errors["title"]
   end
 
   def test_invalid_validator
@@ -1198,7 +1197,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d = Developer.new
       d.salary = "0"
       assert !d.valid?
-      assert_equal "This string contains 'single' and \"double\" quotes", d.errors.on(:salary).last
+      assert_equal "This string contains 'single' and \"double\" quotes", d.errors[:salary].last
     end
   end
 
@@ -1209,7 +1208,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d.name = "John"
       d.name_confirmation = "Johnny"
       assert !d.valid?
-      assert_equal "confirm 'single' and \"double\" quotes", d.errors.on(:name)
+      assert_equal ["confirm 'single' and \"double\" quotes"], d.errors[:name]
     end
   end
 
@@ -1219,7 +1218,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d = Developer.new
       d.name = d.name_confirmation = "John 32"
       assert !d.valid?
-      assert_equal "format 'single' and \"double\" quotes", d.errors.on(:name)
+      assert_equal ["format 'single' and \"double\" quotes"], d.errors[:name]
     end
   end
 
@@ -1229,7 +1228,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d = Developer.new
       d.salary = "90,000"
       assert !d.valid?
-      assert_equal "This string contains 'single' and \"double\" quotes", d.errors.on(:salary).last
+      assert_equal "This string contains 'single' and \"double\" quotes", d.errors[:salary].last
     end
   end
 
@@ -1239,7 +1238,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d = Developer.new
       d.name = "Jeffrey"
       assert !d.valid?
-      assert_equal "This string contains 'single' and \"double\" quotes", d.errors.on(:name)
+      assert_equal ["This string contains 'single' and \"double\" quotes"], d.errors[:name]
     end
   end
 
@@ -1249,7 +1248,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d = Developer.new
       d.name = "Joe"
       assert !d.valid?
-      assert_equal "This string contains 'single' and \"double\" quotes", d.errors.on(:name)
+      assert_equal ["This string contains 'single' and \"double\" quotes"], d.errors[:name]
     end
   end
 
@@ -1259,7 +1258,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d = Developer.new
       d.name = "Joe"
       assert !d.valid?
-      assert_equal "This string contains 'single' and \"double\" quotes", d.errors.on(:name)
+      assert_equal ["This string contains 'single' and \"double\" quotes"], d.errors[:name]
     end
   end
 
@@ -1269,7 +1268,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d = Developer.new
       d.name = "Joe"
       assert !d.valid?
-      assert_equal "This string contains 'single' and \"double\" quotes", d.errors.on(:non_existent)
+      assert_equal ["This string contains 'single' and \"double\" quotes"], d.errors[:non_existent]
     end
   end
 
@@ -1279,7 +1278,7 @@ class ValidationsTest < ActiveRecord::TestCase
       d = Developer.new
       d.name = "David"
       assert !d.valid?
-      assert_equal "This string contains 'single' and \"double\" quotes", d.errors.on(:name)
+      assert_equal ["This string contains 'single' and \"double\" quotes"], d.errors[:name]
     end
   end
 
@@ -1290,7 +1289,7 @@ class ValidationsTest < ActiveRecord::TestCase
       r = Reply.create("title" => "A reply", "content" => "with content!")
       r.topic = Topic.create("title" => "uhohuhoh")
       assert !r.valid?
-      assert_equal "This string contains 'single' and \"double\" quotes", r.errors.on(:topic)
+      assert_equal ["This string contains 'single' and \"double\" quotes"], r.errors[:topic]
     end
   end
 
@@ -1299,8 +1298,8 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}", :if => :condition_is_true )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_unless_validation_using_method_true
@@ -1308,7 +1307,7 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}", :unless => :condition_is_true )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
-    assert !t.errors.on(:title)
+    assert !t.errors[:title].any?
   end
 
   def test_if_validation_using_method_false
@@ -1316,7 +1315,7 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}", :if => :condition_is_true_but_its_not )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
-    assert !t.errors.on(:title)
+    assert t.errors[:title].empty?
   end
 
   def test_unless_validation_using_method_false
@@ -1324,8 +1323,8 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}", :unless => :condition_is_true_but_its_not )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_if_validation_using_string_true
@@ -1333,8 +1332,8 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}", :if => "a = 1; a == 1" )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_unless_validation_using_string_true
@@ -1342,7 +1341,7 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}", :unless => "a = 1; a == 1" )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
-    assert !t.errors.on(:title)
+    assert t.errors[:title].empty?
   end
 
   def test_if_validation_using_string_false
@@ -1350,7 +1349,7 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}", :if => "false")
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
-    assert !t.errors.on(:title)
+    assert t.errors[:title].empty?
   end
 
   def test_unless_validation_using_string_false
@@ -1358,8 +1357,8 @@ class ValidationsTest < ActiveRecord::TestCase
     Topic.validates_length_of( :title, :maximum=>5, :too_long=>"hoo {{count}}", :unless => "false")
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_if_validation_using_block_true
@@ -1368,8 +1367,8 @@ class ValidationsTest < ActiveRecord::TestCase
       :if => Proc.new { |r| r.content.size > 4 } )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_unless_validation_using_block_true
@@ -1378,7 +1377,7 @@ class ValidationsTest < ActiveRecord::TestCase
       :unless => Proc.new { |r| r.content.size > 4 } )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
-    assert !t.errors.on(:title)
+    assert t.errors[:title].empty?
   end
 
   def test_if_validation_using_block_false
@@ -1387,7 +1386,7 @@ class ValidationsTest < ActiveRecord::TestCase
       :if => Proc.new { |r| r.title != "uhohuhoh"} )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert t.valid?
-    assert !t.errors.on(:title)
+    assert t.errors[:title].empty?
   end
 
   def test_unless_validation_using_block_false
@@ -1396,8 +1395,8 @@ class ValidationsTest < ActiveRecord::TestCase
       :unless => Proc.new { |r| r.title != "uhohuhoh"} )
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     assert !t.valid?
-    assert t.errors.on(:title)
-    assert_equal "hoo 5", t.errors["title"]
+    assert t.errors[:title].any?
+    assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_validates_associated_missing
@@ -1405,7 +1404,7 @@ class ValidationsTest < ActiveRecord::TestCase
       Reply.validates_presence_of(:topic)
       r = Reply.create("title" => "A reply", "content" => "with content!")
       assert !r.valid?
-      assert r.errors.on(:topic)
+      assert r.errors[:topic].any?
 
       r.topic = Topic.find :first
       assert r.valid?
@@ -1427,7 +1426,7 @@ class ValidationsTest < ActiveRecord::TestCase
 
      t = Topic.new("title" => "")
      assert !t.valid?
-     assert_equal "can't be blank", t.errors.on("title").first
+     assert_equal "can't be blank", t.errors["title"].first
   end
 
   def test_invalid_should_be_the_opposite_of_valid
@@ -1481,7 +1480,6 @@ class ValidatesNumericalityTest < ActiveRecord::TestCase
 
   def test_default_validates_numericality_of
     Topic.validates_numericality_of :approved
-
     invalid!(NIL + BLANK + JUNK)
     valid!(FLOATS + INTEGERS + BIGDECIMAL + INFINITY)
   end
@@ -1578,11 +1576,11 @@ class ValidatesNumericalityTest < ActiveRecord::TestCase
   end
 
   private
-    def invalid!(values, error=nil)
+    def invalid!(values, error = nil)
       with_each_topic_approved_value(values) do |topic, value|
         assert !topic.valid?, "#{value.inspect} not rejected as a number"
-        assert topic.errors.on(:approved)
-        assert_equal error, topic.errors.on(:approved) if error
+        assert topic.errors[:approved].any?, "FAILED for #{value.inspect}"
+        assert_equal error, topic.errors[:approved].first if error
       end
     end
 
@@ -1593,7 +1591,7 @@ class ValidatesNumericalityTest < ActiveRecord::TestCase
     end
 
     def with_each_topic_approved_value(values)
-      topic = Topic.new("title" => "numeric test", "content" => "whatever")
+      topic = Topic.new(:title => "numeric test", :content => "whatever")
       values.each do |value|
         topic.approved = value
         yield topic, value
diff --git a/activerecord/test/models/reply.rb b/activerecord/test/models/reply.rb
index 1c990acab6..55e7ccd22f 100644
--- a/activerecord/test/models/reply.rb
+++ b/activerecord/test/models/reply.rb
@@ -12,25 +12,25 @@ class Reply < Topic
   attr_accessible :title, :author_name, :author_email_address, :written_on, :content, :last_read
 
   def validate
-    errors.add("title", "Empty")   unless attribute_present? "title"
+    errors[:title] << "Empty" unless attribute_present?("title")
   end
 
   def errors_on_empty_content
-    errors.add("content", "Empty") unless attribute_present? "content"
+    errors[:content] << "Empty" unless attribute_present?("content")
   end
 
   def validate_on_create
     if attribute_present?("title") && attribute_present?("content") && content == "Mismatch"
-      errors.add("title", "is Content Mismatch")
+      errors[:title] << "is Content Mismatch"
     end
   end
 
   def title_is_wrong_create
-    errors.add("title", "is Wrong Create") if attribute_present?("title") && title == "Wrong Create"
+    errors[:title] << "is Wrong Create" if attribute_present?("title") && title == "Wrong Create"
   end
 
   def validate_on_update
-    errors.add("title", "is Wrong Update") if attribute_present?("title") && title == "Wrong Update"
+    errors[:title] << "is Wrong Update" if attribute_present?("title") && title == "Wrong Update"
   end
 end