require 'active_support/core_ext/array/wrap' require 'active_support/core_ext/object/inclusion' module ActiveRecord module Associations # = Active Record Associations # # This is the root class of all associations ('+ Foo' signifies an included module Foo): # # Association # SingularAssociation # HasOneAssociation # HasOneThroughAssociation + ThroughAssociation # BelongsToAssociation # BelongsToPolymorphicAssociation # CollectionAssociation # HasAndBelongsToManyAssociation # HasManyAssociation # HasManyThroughAssociation + ThroughAssociation class Association #:nodoc: attr_reader :owner, :target, :reflection delegate :options, :to => :reflection def initialize(owner, reflection) reflection.check_validity! @target = nil @owner, @reflection = owner, reflection @updated = false reset reset_scope end # Returns the name of the table of the related class: # # post.comments.aliased_table_name # => "comments" # def aliased_table_name reflection.klass.table_name end # Resets the \loaded flag to +false+ and sets the \target to +nil+. def reset @loaded = false IdentityMap.remove(target) if IdentityMap.enabled? && target @target = nil @stale_state = nil end # Reloads the \target and returns +self+ on success. def reload reset reset_scope load_target self unless target.nil? end # Has the \target been already \loaded? def loaded? @loaded end # Asserts the \target has been loaded setting the \loaded flag to +true+. def loaded! @loaded = true @stale_state = stale_state end # The target is stale if the target no longer points to the record(s) that the # relevant foreign_key(s) refers to. If stale, the association accessor method # on the owner will reload the target. It's up to subclasses to implement the # state_state method if relevant. # # Note that if the target has not been loaded, it is not considered stale. def stale_target? loaded? && @stale_state != stale_state end # Sets the target of this association to \target, and the \loaded flag to +true+. def target=(target) @target = target loaded! end def scoped target_scope.merge(association_scope) end # The scope for this association. # # Note that the association_scope is merged into the target_scope only when the # scoped method is called. This is because at that point the call may be surrounded # by scope.scoping { ... } or with_scope { ... } etc, which affects the scope which # actually gets built. def association_scope if klass @association_scope ||= AssociationScope.new(self).scope end end def reset_scope @association_scope = nil end # Set the inverse association, if possible def set_inverse_instance(record) if record && invertible_for?(record) inverse = record.association(inverse_reflection_for(record).name) inverse.target = owner end end # This class of the target. belongs_to polymorphic overrides this to look at the # polymorphic_type field on the owner. def klass reflection.klass end # Can be overridden (i.e. in ThroughAssociation) to merge in other scopes (i.e. the # through association's scope) def target_scope klass.scoped end # Loads the \target if needed and returns it. # # This method is abstract in the sense that it relies on +find_target+, # which is expected to be provided by descendants. # # If the \target is stale(the target no longer points to the record(s) that the # relevant foreign_key(s) refers to.), force reload the \target. # # Otherwise if the \target is already \loaded it is just returned. Thus, you can # call +load_target+ unconditionally to get the \target. # # ActiveRecord::RecordNotFound is rescued within the method, and it is # not reraised. The proxy is \reset and +nil+ is the return value. def load_target if (@stale_state && stale_target?) || find_target? begin if IdentityMap.enabled? && association_class && association_class.respond_to?(:base_class) @target = IdentityMap.get(association_class, owner[reflection.foreign_key]) elsif @stale_state && stale_target? @target = find_target end rescue NameError nil ensure @target ||= find_target end end loaded! unless loaded? target rescue ActiveRecord::RecordNotFound reset end def interpolate(sql, record = nil) if sql.respond_to?(:to_proc) && !sql.is_a?(Hash) owner.send(:instance_exec, record, &sql) else sql end end private def find_target? !loaded? && (!owner.new_record? || foreign_key_present?) && klass end def creation_attributes attributes = {} if reflection.macro.in?([:has_one, :has_many]) && !options[:through] attributes[reflection.foreign_key] = owner[reflection.active_record_primary_key] if reflection.options[:as] attributes[reflection.type] = owner.class.base_class.name end end attributes end # Sets the owner attributes on the given record def set_owner_attributes(record) creation_attributes.each { |key, value| record[key] = value } end # Should be true if there is a foreign key present on the owner which # references the target. This is used to determine whether we can load # the target if the owner is currently a new record (and therefore # without a key). # # Currently implemented by belongs_to (vanilla and polymorphic) and # has_one/has_many :through associations which go through a belongs_to def foreign_key_present? false end # Raises ActiveRecord::AssociationTypeMismatch unless +record+ is of # the kind of the class of the associated objects. Meant to be used as # a sanity check when you are about to assign an associated record. def raise_on_type_mismatch(record) unless record.is_a?(reflection.klass) || record.is_a?(reflection.class_name.constantize) message = "#{reflection.class_name}(##{reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})" raise ActiveRecord::AssociationTypeMismatch, message end end # Can be redefined by subclasses, notably polymorphic belongs_to # The record parameter is necessary to support polymorphic inverses as we must check for # the association in the specific class of the record. def inverse_reflection_for(record) reflection.inverse_of end # Is this association invertible? Can be redefined by subclasses. def invertible_for?(record) inverse_reflection_for(record) end # This should be implemented to return the values of the relevant key(s) on the owner, # so that when state_state is different from the value stored on the last find_target, # the target is stale. # # This is only relevant to certain associations, which is why it returns nil by default. def stale_state end def association_class @reflection.klass end def build_record(attributes, options) reflection.build_association(attributes, options) do |record| skip_assign = [reflection.foreign_key, reflection.type].compact attributes = create_scope.except(*(record.changed - skip_assign)) record.assign_attributes(attributes, :without_protection => true) end end end end end