require 'active_support/core_ext/array/wrap' module ActiveRecord module Associations # = Active Record Associations # # This is the root class of all associations ('+ Foo' signifies an included module Foo): # # Association # SingularAssociation # HasOneAssociation + ForeignAssociation # HasOneThroughAssociation + ThroughAssociation # BelongsToAssociation # BelongsToPolymorphicAssociation # CollectionAssociation # HasManyAssociation + ForeignAssociation # HasManyThroughAssociation + ThroughAssociation class Association #:nodoc: attr_reader :owner, :target, :reflection attr_accessor :inversed delegate :options, :to => :reflection def initialize(owner, reflection) reflection.check_validity! @owner, @reflection = owner, reflection reset reset_scope end # Returns the name of the table of the associated class: # # post.comments.aliased_table_name # => "comments" # def aliased_table_name klass.table_name end # Resets the \loaded flag to +false+ and sets the \target to +nil+. def reset @loaded = false @target = nil @stale_state = nil @inversed = false 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 @inversed = false 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 # stale_state method if relevant. # # Note that if the target has not been loaded, it is not considered stale. def stale_target? !inversed && 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 scope 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 # scope 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.scope(self, klass.connection) end end def reset_scope @association_scope = nil end # Set the inverse association, if possible def set_inverse_instance(record) if invertible_for?(record) inverse = record.association(inverse_reflection_for(record).name) inverse.target = owner inverse.inversed = true end record end # Returns the 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 AssociationRelation.create(klass, klass.arel_table, klass.predicate_builder, self).merge!(klass.all) 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 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 @target = find_target if (@stale_state && stale_target?) || find_target? loaded! unless loaded? target rescue ActiveRecord::RecordNotFound reset end def interpolate(sql, record = nil) if sql.respond_to?(:to_proc) owner.instance_exec(record, &sql) else sql end end # We can't dump @reflection since it contains the scope proc def marshal_dump ivars = (instance_variables - [:@reflection]).map { |name| [name, instance_variable_get(name)] } [@reflection.name, ivars] end def marshal_load(data) reflection_name, ivars = data ivars.each { |name, val| instance_variable_set(name, val) } @reflection = @owner.class._reflect_on_association(reflection_name) end def initialize_attributes(record, except_from_scope_attributes = nil) #:nodoc: except_from_scope_attributes ||= {} skip_assign = [reflection.foreign_key, reflection.type].compact assigned_keys = record.changed assigned_keys += except_from_scope_attributes.keys.map(&:to_s) attributes = create_scope.except(*(assigned_keys - skip_assign)) record.assign_attributes(attributes) set_inverse_instance(record) end private def find_target? !loaded? && (!owner.new_record? || foreign_key_present?) && klass end def creation_attributes attributes = {} if (reflection.has_one? || reflection.collection?) && !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 # Returns 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). If the owner is a new record then foreign_key must # be present in order to load target. # # 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) fresh_class = reflection.class_name.safe_constantize unless fresh_class && record.is_a?(fresh_class) message = "#{reflection.class_name}(##{reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})" raise ActiveRecord::AssociationTypeMismatch, message end 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 # Returns true if inverse association on the given record needs to be set. # This method is redefined by subclasses. def invertible_for?(record) foreign_key_for?(record) && inverse_reflection_for(record) end # Returns true if record contains the foreign_key def foreign_key_for?(record) record.has_attribute?(reflection.foreign_key) end # This should be implemented to return the values of the relevant key(s) on the owner, # so that when stale_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 build_record(attributes) reflection.build_association(attributes) do |record| initialize_attributes(record, attributes) end end # Returns true if statement cache should be skipped on the association reader. def skip_statement_cache? reflection.has_scope? || scope.eager_loading? || klass.scope_attributes? || reflection.source_reflection.active_record.default_scopes.any? end end end end