--- /dev/null
+module ActiveRecord
+ module Reflection # :nodoc:
+ def self.included(base)
+ base.extend(ClassMethods)
+ end
+
+ # Reflection allows you to interrogate Active Record classes and objects about their associations and aggregations.
+ # This information can, for example, be used in a form builder that took an Active Record object and created input
+ # fields for all of the attributes depending on their type and displayed the associations to other objects.
+ #
+ # You can find the interface for the AggregateReflection and AssociationReflection classes in the abstract MacroReflection class.
+ module ClassMethods
+ def create_reflection(macro, name, options, active_record)
+ case macro
+ when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many
+ klass = options[:through] ? ThroughReflection : AssociationReflection
+ reflection = klass.new(macro, name, options, active_record)
+ when :composed_of
+ reflection = AggregateReflection.new(macro, name, options, active_record)
+ end
+ write_inheritable_hash :reflections, name => reflection
+ reflection
+ end
+
+ # Returns a hash containing all AssociationReflection objects for the current class
+ # Example:
+ #
+ # Invoice.reflections
+ # Account.reflections
+ #
+ def reflections
+ read_inheritable_attribute(:reflections) || write_inheritable_attribute(:reflections, {})
+ end
+
+ # Returns an array of AggregateReflection objects for all the aggregations in the class.
+ def reflect_on_all_aggregations
+ reflections.values.select { |reflection| reflection.is_a?(AggregateReflection) }
+ end
+
+ # Returns the AggregateReflection object for the named +aggregation+ (use the symbol). Example:
+ #
+ # Account.reflect_on_aggregation(:balance) # returns the balance AggregateReflection
+ #
+ def reflect_on_aggregation(aggregation)
+ reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil
+ end
+
+ # Returns an array of AssociationReflection objects for all the associations in the class. If you only want to reflect on a
+ # certain association type, pass in the symbol (<tt>:has_many</tt>, <tt>:has_one</tt>, <tt>:belongs_to</tt>) for that as the first parameter.
+ # Example:
+ #
+ # Account.reflect_on_all_associations # returns an array of all associations
+ # Account.reflect_on_all_associations(:has_many) # returns an array of all has_many associations
+ #
+ def reflect_on_all_associations(macro = nil)
+ association_reflections = reflections.values.select { |reflection| reflection.is_a?(AssociationReflection) }
+ macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections
+ end
+
+ # Returns the AssociationReflection object for the named +association+ (use the symbol). Example:
+ #
+ # Account.reflect_on_association(:owner) # returns the owner AssociationReflection
+ # Invoice.reflect_on_association(:line_items).macro # returns :has_many
+ #
+ def reflect_on_association(association)
+ reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil
+ end
+ end
+
+
+ # Abstract base class for AggregateReflection and AssociationReflection that describes the interface available for both of
+ # those classes. Objects of AggregateReflection and AssociationReflection are returned by the Reflection::ClassMethods.
+ class MacroReflection
+ attr_reader :active_record
+
+ def initialize(macro, name, options, active_record)
+ @macro, @name, @options, @active_record = macro, name, options, active_record
+ end
+
+ # Returns the name of the macro. For example, <tt>composed_of :balance, :class_name => 'Money'</tt> will return
+ # <tt>:balance</tt> or for <tt>has_many :clients</tt> it will return <tt>:clients</tt>.
+ def name
+ @name
+ end
+
+ # Returns the macro type. For example, <tt>composed_of :balance, :class_name => 'Money'</tt> will return <tt>:composed_of</tt>
+ # or for <tt>has_many :clients</tt> will return <tt>:has_many</tt>.
+ def macro
+ @macro
+ end
+
+ # Returns the hash of options used for the macro. For example, it would return <tt>{ :class_name => "Money" }</tt> for
+ # <tt>composed_of :balance, :class_name => 'Money'</tt> or +{}+ for <tt>has_many :clients</tt>.
+ def options
+ @options
+ end
+
+ # Returns the class for the macro. For example, <tt>composed_of :balance, :class_name => 'Money'</tt> returns the Money
+ # class and <tt>has_many :clients</tt> returns the Client class.
+ def klass
+ @klass ||= class_name.constantize
+ end
+
+ # Returns the class name for the macro. For example, <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>'Money'</tt>
+ # and <tt>has_many :clients</tt> returns <tt>'Client'</tt>.
+ def class_name
+ @class_name ||= options[:class_name] || derive_class_name
+ end
+
+ # Returns +true+ if +self+ and +other_aggregation+ have the same +name+ attribute, +active_record+ attribute,
+ # and +other_aggregation+ has an options hash assigned to it.
+ def ==(other_aggregation)
+ other_aggregation.kind_of?(self.class) && name == other_aggregation.name && other_aggregation.options && active_record == other_aggregation.active_record
+ end
+
+ def sanitized_conditions #:nodoc:
+ @sanitized_conditions ||= klass.send(:sanitize_sql, options[:conditions]) if options[:conditions]
+ end
+
+ # Returns +true+ if +self+ is a +belongs_to+ reflection.
+ def belongs_to?
+ macro == :belongs_to
+ end
+
+ private
+ def derive_class_name
+ name.to_s.camelize
+ end
+ end
+
+
+ # Holds all the meta-data about an aggregation as it was specified in the Active Record class.
+ class AggregateReflection < MacroReflection #:nodoc:
+ end
+
+ # Holds all the meta-data about an association as it was specified in the Active Record class.
+ class AssociationReflection < MacroReflection #:nodoc:
+ # Returns the target association's class:
+ #
+ # class Author < ActiveRecord::Base
+ # has_many :books
+ # end
+ #
+ # Author.reflect_on_association(:books).klass
+ # # => Book
+ #
+ # <b>Note:</b> do not call +klass.new+ or +klass.create+ to instantiate
+ # a new association object. Use +build_association+ or +create_association+
+ # instead. This allows plugins to hook into association object creation.
+ def klass
+ @klass ||= active_record.send(:compute_type, class_name)
+ end
+
+ # Returns a new, unsaved instance of the associated class. +options+ will
+ # be passed to the class's constructor.
+ def build_association(*options)
+ klass.new(*options)
+ end
+
+ # Creates a new instance of the associated class, and immediates saves it
+ # with ActiveRecord::Base#save. +options+ will be passed to the class's
+ # creation method. Returns the newly created object.
+ def create_association(*options)
+ klass.create(*options)
+ end
+
+ # Creates a new instance of the associated class, and immediates saves it
+ # with ActiveRecord::Base#save!. +options+ will be passed to the class's
+ # creation method. If the created record doesn't pass validations, then an
+ # exception will be raised.
+ #
+ # Returns the newly created object.
+ def create_association!(*options)
+ klass.create!(*options)
+ end
+
+ def table_name
+ @table_name ||= klass.table_name
+ end
+
+ def quoted_table_name
+ @quoted_table_name ||= klass.quoted_table_name
+ end
+
+ def primary_key_name
+ @primary_key_name ||= options[:foreign_key] || derive_primary_key_name
+ end
+
+ def association_foreign_key
+ @association_foreign_key ||= @options[:association_foreign_key] || class_name.foreign_key
+ end
+
+ def counter_cache_column
+ if options[:counter_cache] == true
+ "#{active_record.name.underscore.pluralize}_count"
+ elsif options[:counter_cache]
+ options[:counter_cache]
+ end
+ end
+
+ def check_validity!
+ end
+
+ def through_reflection
+ false
+ end
+
+ def through_reflection_primary_key_name
+ end
+
+ def source_reflection
+ nil
+ end
+
+ private
+ def derive_class_name
+ class_name = name.to_s.camelize
+ class_name = class_name.singularize if [ :has_many, :has_and_belongs_to_many ].include?(macro)
+ class_name
+ end
+
+ def derive_primary_key_name
+ if belongs_to?
+ "#{name}_id"
+ elsif options[:as]
+ "#{options[:as]}_id"
+ else
+ active_record.name.foreign_key
+ end
+ end
+ end
+
+ # Holds all the meta-data about a :through association as it was specified in the Active Record class.
+ class ThroughReflection < AssociationReflection #:nodoc:
+ # Gets the source of the through reflection. It checks both a singularized and pluralized form for <tt>:belongs_to</tt> or <tt>:has_many</tt>.
+ # (The <tt>:tags</tt> association on Tagging below.)
+ #
+ # class Post < ActiveRecord::Base
+ # has_many :taggings
+ # has_many :tags, :through => :taggings
+ # end
+ #
+ def source_reflection
+ @source_reflection ||= source_reflection_names.collect { |name| through_reflection.klass.reflect_on_association(name) }.compact.first
+ end
+
+ # Returns the AssociationReflection object specified in the <tt>:through</tt> option
+ # of a HasManyThrough or HasOneThrough association. Example:
+ #
+ # class Post < ActiveRecord::Base
+ # has_many :taggings
+ # has_many :tags, :through => :taggings
+ # end
+ #
+ # tags_reflection = Post.reflect_on_association(:tags)
+ # taggings_reflection = tags_reflection.through_reflection
+ #
+ def through_reflection
+ @through_reflection ||= active_record.reflect_on_association(options[:through])
+ end
+
+ # Gets an array of possible <tt>:through</tt> source reflection names:
+ #
+ # [:singularized, :pluralized]
+ #
+ def source_reflection_names
+ @source_reflection_names ||= (options[:source] ? [options[:source]] : [name.to_s.singularize, name]).collect { |n| n.to_sym }
+ end
+
+ def check_validity!
+ if through_reflection.nil?
+ raise HasManyThroughAssociationNotFoundError.new(active_record.name, self)
+ end
+
+ if source_reflection.nil?
+ raise HasManyThroughSourceAssociationNotFoundError.new(self)
+ end
+
+ if options[:source_type] && source_reflection.options[:polymorphic].nil?
+ raise HasManyThroughAssociationPointlessSourceTypeError.new(active_record.name, self, source_reflection)
+ end
+
+ if source_reflection.options[:polymorphic] && options[:source_type].nil?
+ raise HasManyThroughAssociationPolymorphicError.new(active_record.name, self, source_reflection)
+ end
+
+ unless [:belongs_to, :has_many].include?(source_reflection.macro) && source_reflection.options[:through].nil?
+ raise HasManyThroughSourceAssociationMacroError.new(self)
+ end
+ end
+
+ def through_reflection_primary_key
+ through_reflection.belongs_to? ? through_reflection.klass.primary_key : through_reflection.primary_key_name
+ end
+
+ def through_reflection_primary_key_name
+ through_reflection.primary_key_name if through_reflection.belongs_to?
+ end
+
+ private
+ def derive_class_name
+ # get the class_name of the belongs_to association of the through reflection
+ options[:source_type] || source_reflection.class_name
+ end
+ end
+ end
+end
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