require 'thread' module ActiveRecord # = Active Record Reflection module Reflection # :nodoc: extend ActiveSupport::Concern included do class_attribute :reflections class_attribute :aggregate_reflections self.reflections = {} self.aggregate_reflections = {} end def self.create(macro, name, scope, options, ar) case macro when :has_many, :belongs_to, :has_one klass = options[:through] ? ThroughReflection : AssociationReflection when :composed_of klass = AggregateReflection end klass.new(macro, name, scope, options, ar) end def self.add_reflection(ar, name, reflection) ar.reflections = ar.reflections.merge(name.to_s => reflection) end def self.add_aggregate_reflection(ar, name, reflection) ar.aggregate_reflections = ar.aggregate_reflections.merge(name.to_s => reflection) end # \Reflection enables to interrogate Active Record classes and objects # about their associations and aggregations. This information can, # for example, be used in a form builder that takes an Active Record object # and creates input fields for all of the attributes depending on their type # and displays the associations to other objects. # # MacroReflection class has info for AggregateReflection and AssociationReflection # classes. module ClassMethods # Returns an array of AggregateReflection objects for all the aggregations in the class. def reflect_on_all_aggregations aggregate_reflections.values end # Returns the AggregateReflection object for the named +aggregation+ (use the symbol). # # Account.reflect_on_aggregation(:balance) # => the balance AggregateReflection # def reflect_on_aggregation(aggregation) aggregate_reflections[aggregation.to_s] 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 (:has_many, :has_one, # :belongs_to) 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 macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections end # Returns the AssociationReflection object for the +association+ (use the symbol). # # 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.to_s] end # Returns an array of AssociationReflection objects for all associations which have :autosave enabled. def reflect_on_all_autosave_associations reflections.values.select { |reflection| reflection.options[:autosave] } end end # Base class for AggregateReflection and AssociationReflection. Objects of # AggregateReflection and AssociationReflection are returned by the Reflection::ClassMethods. # # MacroReflection # AggregateReflection # AssociationReflection # ThroughReflection class MacroReflection # Returns the name of the macro. # # composed_of :balance, class_name: 'Money' returns :balance # has_many :clients returns :clients attr_reader :name # Returns the macro type. # # composed_of :balance, class_name: 'Money' returns :composed_of # has_many :clients returns :has_many attr_reader :macro attr_reader :scope # Returns the hash of options used for the macro. # # composed_of :balance, class_name: 'Money' returns { class_name: "Money" } # has_many :clients returns {} attr_reader :options attr_reader :active_record attr_reader :plural_name # :nodoc: def initialize(macro, name, scope, options, active_record) @macro = macro @name = name @scope = scope @options = options @active_record = active_record @klass = options[:class] @plural_name = active_record.pluralize_table_names ? name.to_s.pluralize : name.to_s end def autosave=(autosave) @automatic_inverse_of = false @options[:autosave] = autosave end # Returns the class for the macro. # # composed_of :balance, class_name: 'Money' returns the Money class # has_many :clients returns the Client class def klass @klass ||= class_name.constantize end # Returns the class name for the macro. # # composed_of :balance, class_name: 'Money' returns 'Money' # has_many :clients returns 'Client' def class_name @class_name ||= (options[:class_name] || derive_class_name).to_s 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) super || other_aggregation.kind_of?(self.class) && name == other_aggregation.name && !other_aggregation.options.nil? && active_record == other_aggregation.active_record 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: def mapping mapping = options[:mapping] || [name, name] mapping.first.is_a?(Array) ? mapping : [mapping] end 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 # # Note: 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 attr_reader :type, :foreign_type def initialize(macro, name, scope, options, active_record) super @collection = :has_many == macro @automatic_inverse_of = nil @type = options[:as] && "#{options[:as]}_type" @foreign_type = options[:foreign_type] || "#{name}_type" @constructable = calculate_constructable(macro, options) @association_scope_cache = {} @scope_lock = Mutex.new end def association_scope_cache(conn, owner) key = conn.prepared_statements if options[:polymorphic] key = [key, owner.read_attribute(@foreign_type)] end @association_scope_cache[key] ||= @scope_lock.synchronize { @association_scope_cache[key] ||= yield } end # Returns a new, unsaved instance of the associated class. +attributes+ will # be passed to the class's constructor. def build_association(attributes, &block) klass.new(attributes, &block) end def constructable? # :nodoc: @constructable end def table_name klass.table_name end def quoted_table_name klass.quoted_table_name end def join_table @join_table ||= options[:join_table] || derive_join_table end def foreign_key @foreign_key ||= options[:foreign_key] || derive_foreign_key end def primary_key_column klass.columns_hash[klass.primary_key] end def association_foreign_key @association_foreign_key ||= options[:association_foreign_key] || class_name.foreign_key end # klass option is necessary to support loading polymorphic associations def association_primary_key(klass = nil) options[:primary_key] || primary_key(klass || self.klass) end def active_record_primary_key @active_record_primary_key ||= options[:primary_key] || primary_key(active_record) end def counter_cache_column if options[:counter_cache] == true "#{active_record.name.demodulize.underscore.pluralize}_count" elsif options[:counter_cache] options[:counter_cache].to_s end end def check_validity! check_validity_of_inverse! end def check_validity_of_inverse! unless options[:polymorphic] if has_inverse? && inverse_of.nil? raise InverseOfAssociationNotFoundError.new(self) end end end def check_preloadable! return unless scope if scope.arity > 0 ActiveSupport::Deprecation.warn <<-WARNING The association scope '#{name}' is instance dependent (the scope block takes an argument). Preloading happens before the individual instances are created. This means that there is no instance being passed to the association scope. This will most likely result in broken or incorrect behavior. Joining, Preloading and eager loading of these associations is deprecated and will be removed in the future. WARNING end end alias :check_eager_loadable! :check_preloadable! def join_id_for(owner) #:nodoc: key = (source_macro == :belongs_to) ? foreign_key : active_record_primary_key owner[key] end def through_reflection nil end def source_reflection self end # A chain of reflections from this one back to the owner. For more see the explanation in # ThroughReflection. def chain [self] end def nested? false end # An array of arrays of scopes. Each item in the outside array corresponds to a reflection # in the #chain. def scope_chain scope ? [[scope]] : [[]] end alias :source_macro :macro def has_inverse? inverse_name end def inverse_of return unless inverse_name @inverse_of ||= klass.reflect_on_association inverse_name end def polymorphic_inverse_of(associated_class) if has_inverse? if inverse_relationship = associated_class.reflect_on_association(options[:inverse_of]) inverse_relationship else raise InverseOfAssociationNotFoundError.new(self, associated_class) end end end # Returns whether or not this association reflection is for a collection # association. Returns +true+ if the +macro+ is either +has_many+ or # +has_and_belongs_to_many+, +false+ otherwise. def collection? @collection end # Returns whether or not the association should be validated as part of # the parent's validation. # # Unless you explicitly disable validation with # validate: false, validation will take place when: # # * you explicitly enable validation; validate: true # * you use autosave; autosave: true # * the association is a +has_many+ association def validate? !options[:validate].nil? ? options[:validate] : (options[:autosave] == true || macro == :has_many) end # Returns +true+ if +self+ is a +belongs_to+ reflection. def belongs_to? macro == :belongs_to end def association_class case macro when :belongs_to if options[:polymorphic] Associations::BelongsToPolymorphicAssociation else Associations::BelongsToAssociation end when :has_many if options[:through] Associations::HasManyThroughAssociation else Associations::HasManyAssociation end when :has_one if options[:through] Associations::HasOneThroughAssociation else Associations::HasOneAssociation end end end def polymorphic? options.key? :polymorphic end VALID_AUTOMATIC_INVERSE_MACROS = [:has_many, :has_one, :belongs_to] INVALID_AUTOMATIC_INVERSE_OPTIONS = [:conditions, :through, :polymorphic, :foreign_key] protected def actual_source_reflection # FIXME: this is a horrible name self end private def calculate_constructable(macro, options) case macro when :belongs_to !options[:polymorphic] when :has_one !options[:through] else true end end # Attempts to find the inverse association name automatically. # If it cannot find a suitable inverse association name, it returns # nil. def inverse_name options.fetch(:inverse_of) do if @automatic_inverse_of == false nil else @automatic_inverse_of ||= automatic_inverse_of end end end # returns either nil or the inverse association name that it finds. def automatic_inverse_of if can_find_inverse_of_automatically?(self) inverse_name = ActiveSupport::Inflector.underscore(active_record.name).to_sym begin reflection = klass.reflect_on_association(inverse_name) rescue NameError # Give up: we couldn't compute the klass type so we won't be able # to find any associations either. reflection = false end if valid_inverse_reflection?(reflection) return inverse_name end end false end # Checks if the inverse reflection that is returned from the # +automatic_inverse_of+ method is a valid reflection. We must # make sure that the reflection's active_record name matches up # with the current reflection's klass name. # # Note: klass will always be valid because when there's a NameError # from calling +klass+, +reflection+ will already be set to false. def valid_inverse_reflection?(reflection) reflection && klass.name == reflection.active_record.name && can_find_inverse_of_automatically?(reflection) end # Checks to see if the reflection doesn't have any options that prevent # us from being able to guess the inverse automatically. First, the # inverse_of option cannot be set to false. Second, we must # have has_many, has_one, belongs_to associations. # Third, we must not have options such as :polymorphic or # :foreign_key which prevent us from correctly guessing the # inverse association. # # Anything with a scope can additionally ruin our attempt at finding an # inverse, so we exclude reflections with scopes. def can_find_inverse_of_automatically?(reflection) reflection.options[:inverse_of] != false && VALID_AUTOMATIC_INVERSE_MACROS.include?(reflection.macro) && !INVALID_AUTOMATIC_INVERSE_OPTIONS.any? { |opt| reflection.options[opt] } && !reflection.scope end def derive_class_name class_name = name.to_s class_name = class_name.singularize if collection? class_name.camelize end def derive_foreign_key if belongs_to? "#{name}_id" elsif options[:as] "#{options[:as]}_id" else active_record.name.foreign_key end end def derive_join_table [active_record.table_name, klass.table_name].sort.join("\0").gsub(/^(.*_)(.+)\0\1(.+)/, '\1\2_\3').gsub("\0", "_") end def primary_key(klass) klass.primary_key || raise(UnknownPrimaryKey.new(klass)) end end # Holds all the meta-data about a :through association as it was specified # in the Active Record class. class ThroughReflection < AssociationReflection #:nodoc: delegate :foreign_key, :foreign_type, :association_foreign_key, :active_record_primary_key, :type, :to => :source_reflection def initialize(macro, name, scope, options, active_record) super @source_reflection_name = options[:source] end # Returns the source of the through reflection. It checks both a singularized # and pluralized form for :belongs_to or :has_many. # # class Post < ActiveRecord::Base # has_many :taggings # has_many :tags, through: :taggings # end # # class Tagging < ActiveRecord::Base # belongs_to :post # belongs_to :tag # end # # tags_reflection = Post.reflect_on_association(:tags) # tags_reflection.source_reflection # # => # def source_reflection through_reflection.klass.reflect_on_association(source_reflection_name) end # Returns the AssociationReflection object specified in the :through option # of a HasManyThrough or HasOneThrough association. # # class Post < ActiveRecord::Base # has_many :taggings # has_many :tags, through: :taggings # end # # tags_reflection = Post.reflect_on_association(:tags) # tags_reflection.through_reflection # # => # def through_reflection active_record.reflect_on_association(options[:through]) end # Returns an array of reflections which are involved in this association. Each item in the # array corresponds to a table which will be part of the query for this association. # # The chain is built by recursively calling #chain on the source reflection and the through # reflection. The base case for the recursion is a normal association, which just returns # [self] as its #chain. # # class Post < ActiveRecord::Base # has_many :taggings # has_many :tags, through: :taggings # end # # tags_reflection = Post.reflect_on_association(:tags) # tags_reflection.chain # # => [:taggings}, @active_record=Post>, # ] # def chain @chain ||= begin a = source_reflection.chain b = through_reflection.chain chain = a + b chain[0] = self # Use self so we don't lose the information from :source_type chain end end # Consider the following example: # # class Person # has_many :articles # has_many :comment_tags, through: :articles # end # # class Article # has_many :comments # has_many :comment_tags, through: :comments, source: :tags # end # # class Comment # has_many :tags # end # # There may be scopes on Person.comment_tags, Article.comment_tags and/or Comment.tags, # but only Comment.tags will be represented in the #chain. So this method creates an array # of scopes corresponding to the chain. def scope_chain @scope_chain ||= begin scope_chain = source_reflection.scope_chain.map(&:dup) # Add to it the scope from this reflection (if any) scope_chain.first << scope if scope through_scope_chain = through_reflection.scope_chain.map(&:dup) if options[:source_type] through_scope_chain.first << through_reflection.klass.where(foreign_type => options[:source_type]) end # Recursively fill out the rest of the array from the through reflection scope_chain + through_scope_chain end end # The macro used by the source association def source_macro source_reflection.source_macro end # A through association is nested if there would be more than one join table def nested? chain.length > 2 end # We want to use the klass from this reflection, rather than just delegate straight to # the source_reflection, because the source_reflection may be polymorphic. We still # need to respect the source_reflection's :primary_key option, though. def association_primary_key(klass = nil) # Get the "actual" source reflection if the immediate source reflection has a # source reflection itself actual_source_reflection.options[:primary_key] || primary_key(klass || self.klass) end # Gets an array of possible :through source reflection names in both singular and plural form. # # class Post < ActiveRecord::Base # has_many :taggings # has_many :tags, through: :taggings # end # # tags_reflection = Post.reflect_on_association(:tags) # tags_reflection.source_reflection_names # # => [:tag, :tags] # def source_reflection_names options[:source] ? [options[:source]] : [name.to_s.singularize, name].uniq end def source_reflection_name # :nodoc: return @source_reflection_name if @source_reflection_name names = [name.to_s.singularize, name].collect { |n| n.to_sym }.uniq names = names.find_all { |n| through_reflection.klass.reflect_on_association(n) } if names.length > 1 example_options = options.dup example_options[:source] = source_reflection_names.first ActiveSupport::Deprecation.warn <<-eowarn Ambiguous source reflection for through association. Please specify a :source directive on your declaration like: class #{active_record.name} < ActiveRecord::Base #{macro} :#{name}, #{example_options} end eowarn end @source_reflection_name = names.first end def source_options source_reflection.options end def through_options through_reflection.options end def check_validity! if through_reflection.nil? raise HasManyThroughAssociationNotFoundError.new(active_record.name, self) end if through_reflection.options[:polymorphic] raise HasManyThroughAssociationPolymorphicThroughError.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 HasManyThroughAssociationPolymorphicSourceError.new(active_record.name, self, source_reflection) end if macro == :has_one && through_reflection.collection? raise HasOneThroughCantAssociateThroughCollection.new(active_record.name, self, through_reflection) end check_validity_of_inverse! end protected def actual_source_reflection # FIXME: this is a horrible name source_reflection.actual_source_reflection 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