update AR::AttributeMethods documentation [ci skip]

1 files changed, 124 insertions, 23 deletions

diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index 0aff2562b8..008696f6de 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -2,7 +2,7 @@ require 'active_support/core_ext/enumerable'
 
 module ActiveRecord
   # = Active Record Attribute Methods
-  module AttributeMethods #:nodoc:
+  module AttributeMethods
     extend ActiveSupport::Concern
     include ActiveModel::AttributeMethods
 
@@ -20,7 +20,7 @@ module ActiveRecord
     module ClassMethods
       # Generates all the attribute related methods for columns in the database
       # accessors, mutators and query methods.
-      def define_attribute_methods
+      def define_attribute_methods # :nodoc:
         # Use a mutex; we don't want two thread simaltaneously trying to define
         # attribute methods.
         @attribute_methods_mutex.synchronize do
@@ -31,15 +31,29 @@ module ActiveRecord
         end
       end
 
-      def attribute_methods_generated?
+      def attribute_methods_generated? # :nodoc:
         @attribute_methods_generated ||= false
       end
 
-      def undefine_attribute_methods
+      def undefine_attribute_methods # :nodoc:
         super if attribute_methods_generated?
         @attribute_methods_generated = false
       end
 
+      # Raises a <tt>ActiveRecord::DangerousAttributeError</tt> exception when an
+      # \Active \Record method is defined in the model, otherwise +false+.
+      #
+      #   class Person < ActiveRecord::Base
+      #     def save
+      #       'already defined by Active Record'
+      #     end
+      #   end
+      #
+      #   Person.instance_method_already_implemented?(:save)
+      #   # => ActiveRecord::DangerousAttributeError: save is defined by ActiveRecord
+      #
+      #   Person.instance_method_already_implemented?(:name)
+      #   # => false
       def instance_method_already_implemented?(method_name)
         if dangerous_attribute_method?(method_name)
           raise DangerousAttributeError, "#{method_name} is defined by ActiveRecord"
@@ -56,11 +70,11 @@ module ActiveRecord
 
       # A method name is 'dangerous' if it is already defined by Active Record, but
       # not by any ancestors. (So 'puts' is not dangerous but 'save' is.)
-      def dangerous_attribute_method?(name)
+      def dangerous_attribute_method?(name) # :nodoc:
         method_defined_within?(name, Base)
       end
 
-      def method_defined_within?(name, klass, sup = klass.superclass)
+      def method_defined_within?(name, klass, sup = klass.superclass) # :nodoc:
         if klass.method_defined?(name) || klass.private_method_defined?(name)
           if sup.method_defined?(name) || sup.private_method_defined?(name)
             klass.instance_method(name).owner != sup.instance_method(name).owner
@@ -72,13 +86,27 @@ module ActiveRecord
         end
       end
 
+      # Returns +true+ if +attribute+ is an attribute method and table exists,
+      # +false+ otherwise.
+      #
+      #   class Person < ActiveRecord::Base
+      #   end
+      #
+      #   Person.attribute_method?('name')   # => true
+      #   Person.attribute_method?(:age=)    # => true
+      #   Person.attribute_method?(:nothing) # => false
       def attribute_method?(attribute)
         super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, '')))
       end
 
-      # Returns an array of column names as strings if it's not
-      # an abstract class and table exists.
-      # Otherwise it returns an empty array.
+      # Returns an array of column names as strings if it's not an abstract class and
+      # table exists. Otherwise it returns an empty array.
+      #
+      #   class Person < ActiveRecord::Base
+      #   end
+      #
+      #   Person.attribute_names
+      #   # => ["id", "created_at", "updated_at", "name", "age"]
       def attribute_names
         @attribute_names ||= if !abstract_class? && table_exists?
             column_names
@@ -90,7 +118,7 @@ module ActiveRecord
 
     # If we haven't generated any methods yet, generate them, then
     # see if we've created the method we're looking for.
-    def method_missing(method, *args, &block)
+    def method_missing(method, *args, &block) # :nodoc:
       unless self.class.attribute_methods_generated?
         self.class.define_attribute_methods
 
@@ -104,7 +132,7 @@ module ActiveRecord
       end
     end
 
-    def attribute_missing(match, *args, &block)
+    def attribute_missing(match, *args, &block) # :nodoc:
       if self.class.columns_hash[match.attr_name]
         ActiveSupport::Deprecation.warn(
           "The method `#{match.method_name}', matching the attribute `#{match.attr_name}' has " \
@@ -118,22 +146,60 @@ module ActiveRecord
       super
     end
 
+    # A Person object with a name attribute can ask <tt>person.respond_to?(:name)</tt>,
+    # <tt>person.respond_to?(:name=)</tt>, and <tt>person.respond_to?(:name?)</tt>
+    # which will all return +true+. It also define the attribute methods if they have
+    # not been generated.
+    #
+    #   class Person < ActiveRecord::Base
+    #   end
+    #
+    #   person = Person.new
+    #   person.respond_to(:name)    # => true
+    #   person.respond_to(:name=)   # => true
+    #   person.respond_to(:name?)   # => true
+    #   person.respond_to('age')    # => true
+    #   person.respond_to('age=')   # => true
+    #   person.respond_to('age?')   # => true
+    #   person.respond_to(:nothing) # => false
     def respond_to?(name, include_private = false)
       self.class.define_attribute_methods unless self.class.attribute_methods_generated?
       super
     end
 
-    # Returns true if the given attribute is in the attributes hash
+    # Returns +true+ if the given attribute is in the attributes hash, otherwise +false+.
+    #
+    #   class Person < ActiveRecord::Base
+    #   end
+    #
+    #   person = Person.new
+    #   person.has_attribute?(:name)    # => true
+    #   person.has_attribute?('age')    # => true
+    #   person.has_attribute?(:nothing) # => false
     def has_attribute?(attr_name)
       @attributes.has_key?(attr_name.to_s)
     end
 
     # Returns an array of names for the attributes available on this object.
+    #
+    #   class Person < ActiveRecord::Base
+    #   end
+    #
+    #   person = Person.new
+    #   person.attribute_names
+    #   # => ["id", "created_at", "updated_at", "name", "age"]
     def attribute_names
       @attributes.keys
     end
 
     # Returns a hash of all the attributes with their names as keys and the values of the attributes as values.
+    #
+    #   class Person < ActiveRecord::Base
+    #   end
+    #
+    #   person = Person.create(name: 'Francesco', age: 22)
+    #   person.attributes
+    #   # => {"id"=>3, "created_at"=>Sun, 21 Oct 2012 04:53:04, "updated_at"=>Sun, 21 Oct 2012 04:53:04, "name"=>"Francesco", "age"=>22}
     def attributes
       attribute_names.each_with_object({}) { |name, attrs|
         attrs[name] = read_attribute(name)
@@ -146,7 +212,7 @@ module ActiveRecord
     # <tt>:db</tt> format. Other attributes return the value of
     # <tt>#inspect</tt> without modification.
     #
-    #   person = Person.create!(:name => "David Heinemeier Hansson " * 3)
+    #   person = Person.create!(name: 'David Heinemeier Hansson ' * 3)
     #
     #   person.attribute_for_inspect(:name)
     #   # => '"David Heinemeier Hansson David Heinemeier Hansson D..."'
@@ -165,14 +231,34 @@ module ActiveRecord
       end
     end
 
-    # Returns true if the specified +attribute+ has been set by the user or by a database load and is neither
-    # nil nor empty? (the latter only applies to objects that respond to empty?, most notably Strings).
+    # Returns +true+ if the specified +attribute+ has been set by the user or by a
+    # database load and is neither +nil+ nor <tt>empty?</tt> (the latter only applies
+    # to objects that respond to <tt>empty?</tt>, most notably Strings). Otherwise, +false+.
+    #
+    #   class Person < ActiveRecord::Base
+    #   end
+    #
+    #   person = Person.new(name: '')
+    #   person.attribute_present?(:name) # => false
+    #   person.name = 'Francesco'
+    #   person.attribute_present?(:name) # => true
     def attribute_present?(attribute)
       value = read_attribute(attribute)
       !value.nil? && !(value.respond_to?(:empty?) && value.empty?)
     end
 
-    # Returns the column object for the named attribute.
+    # Returns the column object for the named attribute. Returns +nil+ if the
+    # named attribute not exists.
+    #
+    #   class Person < ActiveRecord::Base
+    #   end
+    #
+    #   person = Person.new
+    #   person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
+    #   # => #<ActiveRecord::ConnectionAdapters::SQLite3Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>
+    #
+    #   person.column_for_attribute(:nothing)
+    #   # => nil
     def column_for_attribute(name)
       # FIXME: should this return a null object for columns that don't exist?
       self.class.columns_hash[name.to_s]
@@ -180,42 +266,57 @@ module ActiveRecord
 
     # Returns the value of the attribute identified by <tt>attr_name</tt> after it has been typecast (for example,
     # "2004-12-12" in a data column is cast to a date object, like Date.new(2004, 12, 12)).
-    # (Alias for the protected read_attribute method).
+    # (Alias for the protected <tt>read_attribute</tt> method).
+    #
+    #   class Person < ActiveRecord::Base
+    #   end
+    #
+    #   person = Person.new(name: 'Francesco', age: '22'
+    #   person[:name] # => "Francesco"
+    #   person[:age]  # => 22
     def [](attr_name)
       read_attribute(attr_name)
     end
 
     # Updates the attribute identified by <tt>attr_name</tt> with the specified +value+.
-    # (Alias for the protected write_attribute method).
+    # (Alias for the protected <tt>write_attribute</tt> method).
+    #
+    #   class Person < ActiveRecord::Base
+    #   end
+    #
+    #   person = Person.new
+    #   person[:age] = '22'
+    #   person[:age] # => 22
+    #   person[:age] # => Fixnum
     def []=(attr_name, value)
       write_attribute(attr_name, value)
     end
 
     protected
 
-    def clone_attributes(reader_method = :read_attribute, attributes = {})
+    def clone_attributes(reader_method = :read_attribute, attributes = {}) # :nodoc:
       attribute_names.each do |name|
         attributes[name] = clone_attribute_value(reader_method, name)
       end
       attributes
     end
 
-    def clone_attribute_value(reader_method, attribute_name)
+    def clone_attribute_value(reader_method, attribute_name) # :nodoc:
       value = send(reader_method, attribute_name)
       value.duplicable? ? value.clone : value
     rescue TypeError, NoMethodError
       value
     end
 
-    def arel_attributes_with_values_for_create(attribute_names)
+    def arel_attributes_with_values_for_create(attribute_names) # :nodoc:
       arel_attributes_with_values(attributes_for_create(attribute_names))
     end
 
-    def arel_attributes_with_values_for_update(attribute_names)
+    def arel_attributes_with_values_for_update(attribute_names) # :nodoc:
       arel_attributes_with_values(attributes_for_update(attribute_names))
     end
 
-    def attribute_method?(attr_name)
+    def attribute_method?(attr_name) # :nodoc:
       defined?(@attributes) && @attributes.include?(attr_name)
     end