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require 'active_support/core_ext/enumerable'
module ActiveRecord
module AttributeMethods #:nodoc:
extend ActiveSupport::Concern
# Declare and check for suffixed attribute methods.
module ClassMethods
# Declares a method available for all attributes with the given suffix.
# Uses +method_missing+ and <tt>respond_to?</tt> to rewrite the method
#
# #{attr}#{suffix}(*args, &block)
#
# to
#
# attribute#{suffix}(#{attr}, *args, &block)
#
# An <tt>attribute#{suffix}</tt> instance method must exist and accept at least
# the +attr+ argument.
#
# For example:
#
# class Person < ActiveRecord::Base
# attribute_method_suffix '_changed?'
#
# private
# def attribute_changed?(attr)
# ...
# end
# end
#
# person = Person.find(1)
# person.name_changed? # => false
# person.name = 'Hubert'
# person.name_changed? # => true
def attribute_method_suffix(*suffixes)
attribute_method_suffixes.concat(suffixes)
rebuild_attribute_method_regexp
undefine_attribute_methods
end
# Defines an "attribute" method (like +inheritance_column+ or
# +table_name+). A new (class) method will be created with the
# given name. If a value is specified, the new method will
# return that value (as a string). Otherwise, the given block
# will be used to compute the value of the method.
#
# The original method will be aliased, with the new name being
# prefixed with "original_". This allows the new method to
# access the original value.
#
# Example:
#
# class A < ActiveRecord::Base
# define_attr_method :primary_key, "sysid"
# define_attr_method( :inheritance_column ) do
# original_inheritance_column + "_id"
# end
# end
def define_attr_method(name, value=nil, &block)
sing = metaclass
sing.send :alias_method, "original_#{name}", name
if block_given?
sing.send :define_method, name, &block
else
# use eval instead of a block to work around a memory leak in dev
# mode in fcgi
sing.class_eval "def #{name}; #{value.to_s.inspect}; end"
end
end
# Returns MatchData if method_name is an attribute method.
def match_attribute_method?(method_name)
rebuild_attribute_method_regexp unless defined?(@@attribute_method_regexp) && @@attribute_method_regexp
@@attribute_method_regexp.match(method_name)
end
# Contains the names of the generated attribute methods.
def generated_methods #:nodoc:
@generated_methods ||= Set.new
end
def generated_methods?
!generated_methods.empty?
end
# Generates all the attribute related methods for columns in the database
# accessors, mutators and query methods.
def define_attribute_methods
return if generated_methods?
columns_hash.keys.each do |name|
attribute_method_suffixes.each do |suffix|
method_name = "#{name}#{suffix}"
unless instance_method_already_implemented?(method_name)
generate_method = "define_attribute_method#{suffix}"
if respond_to?(generate_method)
send(generate_method, name)
else
evaluate_attribute_method("def #{method_name}(*args); send(:attribute#{suffix}, '#{name}', *args); end", method_name)
end
end
end
end
end
def undefine_attribute_methods
generated_methods.each { |name| undef_method(name) }
@generated_methods = nil
end
# Checks whether the method is defined in the model or any of its subclasses
# that also derive from Active Record. Raises DangerousAttributeError if the
# method is defined by Active Record though.
def instance_method_already_implemented?(method_name)
method_name = method_name.to_s
@_defined_class_methods ||= ancestors.first(ancestors.index(ActiveRecord::Base)).sum([]) { |m| m.public_instance_methods(false) | m.private_instance_methods(false) | m.protected_instance_methods(false) }.map {|m| m.to_s }.to_set
@@_defined_activerecord_methods ||= (ActiveRecord::Base.public_instance_methods(false) | ActiveRecord::Base.private_instance_methods(false) | ActiveRecord::Base.protected_instance_methods(false)).map{|m| m.to_s }.to_set
raise DangerousAttributeError, "#{method_name} is defined by ActiveRecord" if @@_defined_activerecord_methods.include?(method_name)
@_defined_class_methods.include?(method_name)
end
private
# Suffixes a, ?, c become regexp /(a|\?|c)$/
def rebuild_attribute_method_regexp
suffixes = attribute_method_suffixes.map { |s| Regexp.escape(s) }
@@attribute_method_regexp = /(#{suffixes.join('|')})$/.freeze
end
def attribute_method_suffixes
@@attribute_method_suffixes ||= []
end
# Evaluate the definition for an attribute related method
def evaluate_attribute_method(method_definition, method_name)
generated_methods << method_name.to_s
begin
class_eval(method_definition, __FILE__, __LINE__)
rescue SyntaxError => err
generated_methods.delete(method_name.to_s)
if logger
logger.warn "Exception occurred during reader method compilation."
logger.warn "Maybe #{method_name} is not a valid Ruby identifier?"
logger.warn err.message
end
end
end
end
# Allows access to the object attributes, which are held in the <tt>@attributes</tt> hash, as though they
# were first-class methods. So a Person class with a name attribute can use Person#name and
# Person#name= and never directly use the attributes hash -- except for multiple assigns with
# ActiveRecord#attributes=. A Milestone class can also ask Milestone#completed? to test that
# the completed attribute is not +nil+ or 0.
#
# It's also possible to instantiate related objects, so a Client class belonging to the clients
# table with a +master_id+ foreign key can instantiate master through Client#master.
def method_missing(method_id, *args, &block)
method_name = method_id.to_s
# If we haven't generated any methods yet, generate them, then
# see if we've created the method we're looking for.
if !self.class.generated_methods?
self.class.define_attribute_methods
guard_private_attribute_method!(method_name, args)
if self.class.generated_methods.include?(method_name)
return self.send(method_id, *args, &block)
end
end
if md = self.class.match_attribute_method?(method_name)
attribute_name, method_type = md.pre_match, md.to_s
if attribute_name == 'id' || @attributes.include?(attribute_name)
guard_private_attribute_method!(method_name, args)
return __send__("attribute#{method_type}", attribute_name, *args, &block)
end
end
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+.
alias :respond_to_without_attributes? :respond_to?
def respond_to?(method, include_private_methods = false)
method_name = method.to_s
if super
return true
elsif !include_private_methods && super(method, true)
# If we're here than we haven't found among non-private methods
# but found among all methods. Which means that given method is private.
return false
elsif !self.class.generated_methods?
self.class.define_attribute_methods
if self.class.generated_methods.include?(method_name)
return true
end
end
if md = self.class.match_attribute_method?(method_name)
return true if md.pre_match == 'id' || @attributes.include?(md.pre_match)
end
super
end
private
# prevent method_missing from calling private methods with #send
def guard_private_attribute_method!(method_name, args)
if self.class.private_method_defined?(method_name)
raise NoMethodError.new("Attempt to call private method", method_name, args)
end
end
def missing_attribute(attr_name, stack)
raise ActiveRecord::MissingAttributeError, "missing attribute: #{attr_name}", stack
end
end
end
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