module ActiveRecord module Reflection # :nodoc: def self.append_features(base) super base.extend(ClassMethods) base.class_eval do class << self alias_method :composed_of_without_reflection, :composed_of def composed_of_with_reflection(part_id, options = {}) composed_of_without_reflection(part_id, options) write_inheritable_array "aggregations", [ AggregateReflection.new(:composed_of, part_id, options, self) ] end alias_method :composed_of, :composed_of_with_reflection end end for association_type in %w( belongs_to has_one has_many has_and_belongs_to_many ) base.module_eval <<-"end_eval" class << self alias_method :#{association_type}_without_reflection, :#{association_type} def #{association_type}_with_reflection(association_id, options = {}) #{association_type}_without_reflection(association_id, options) write_inheritable_array "associations", [ AssociationReflection.new(:#{association_type}, association_id, options, self) ] end alias_method :#{association_type}, :#{association_type}_with_reflection end end_eval end 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 # Returns an array of AggregateReflection objects for all the aggregations in the class. def reflect_on_all_aggregations read_inheritable_attribute "aggregations" 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) reflect_on_all_aggregations.find { |reflection| reflection.name == aggregation } unless reflect_on_all_aggregations.nil? end # Returns an array of AssociationReflection objects for all the aggregations in the class. def reflect_on_all_associations read_inheritable_attribute "associations" end # Returns the AssociationReflection object for the named +aggregation+ (use the symbol). Example: # Account.reflect_on_association(:owner) # returns the owner AssociationReflection def reflect_on_association(association) reflect_on_all_associations.find { |reflection| reflection.name == association } unless reflect_on_all_associations.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, so it would return :balance for "composed_of :balance, :class_name => 'Money'" or # :clients for "has_many :clients". def name @name end # Returns the name of the macro, so it would return :composed_of for # "composed_of :balance, :class_name => 'Money'" or :has_many for "has_many :clients". def macro @macro end # Returns the hash of options used for the macro, so it would return { :class_name => "Money" } for # "composed_of :balance, :class_name => 'Money'" or {} for "has_many :clients". def options @options end # Returns the class for the macro, so "composed_of :balance, :class_name => 'Money'" would return the Money class and # "has_many :clients" would return the Client class. def klass() end def ==(other_aggregation) name == other_aggregation.name && other_aggregation.options && active_record == other_aggregation.active_record end end # Holds all the meta-data about an aggregation as it was specified in the Active Record class. class AggregateReflection < MacroReflection #:nodoc: def klass Object.const_get(options[:class_name] || name_to_class_name(name.id2name)) end private def name_to_class_name(name) name.capitalize.gsub(/_(.)/) { |s| $1.capitalize } end end # Holds all the meta-data about an association as it was specified in the Active Record class. class AssociationReflection < MacroReflection #:nodoc: def klass active_record.send(:compute_type, (name_to_class_name(name.id2name))) end private def name_to_class_name(name) if name !~ /::/ class_name = active_record.send( :type_name_with_module, (options[:class_name] || active_record.class_name(active_record.table_name_prefix + name + active_record.table_name_suffix)) ) end return class_name || name end end end end