Organize Serializer concerns into concerns/

lib/active_model/serializer/concerns/associations.rb

@@ -0,0 +1,100 @@
+module ActiveModel
+  class Serializer
+    # Defines an association in the object should be rendered.
+    #
+    # The serializer object should implement the association name
+    # as a method which should return an array when invoked. If a method
+    # with the association name does not exist, the association name is
+    # dispatched to the serialized object.
+    #
+    module Associations
+      extend ActiveSupport::Concern
+
+      included do
+        with_options instance_writer: false, instance_reader: true do |serializer|
+          serializer.class_attribute :_reflections
+          self._reflections ||= {}
+        end
+
+        extend ActiveSupport::Autoload
+        autoload :Association
+        autoload :Reflection
+        autoload :SingularReflection
+        autoload :CollectionReflection
+        autoload :BelongsToReflection
+        autoload :HasOneReflection
+        autoload :HasManyReflection
+      end
+
+      module ClassMethods
+        def inherited(base)
+          super
+          base._reflections = _reflections.dup
+        end
+
+        # @param [Symbol] name of the association
+        # @param [Hash<Symbol => any>] options for the reflection
+        # @return [void]
+        #
+        # @example
+        #  has_many :comments, serializer: CommentSummarySerializer
+        #
+        def has_many(name, options = {}, &block) # rubocop:disable Style/PredicateName
+          associate(HasManyReflection.new(name, options, block))
+        end
+
+        # @param [Symbol] name of the association
+        # @param [Hash<Symbol => any>] options for the reflection
+        # @return [void]
+        #
+        # @example
+        #  belongs_to :author, serializer: AuthorSerializer
+        #
+        def belongs_to(name, options = {}, &block)
+          associate(BelongsToReflection.new(name, options, block))
+        end
+
+        # @param [Symbol] name of the association
+        # @param [Hash<Symbol => any>] options for the reflection
+        # @return [void]
+        #
+        # @example
+        #  has_one :author, serializer: AuthorSerializer
+        #
+        def has_one(name, options = {}, &block) # rubocop:disable Style/PredicateName
+          associate(HasOneReflection.new(name, options, block))
+        end
+
+        private
+
+        # Add reflection and define {name} accessor.
+        # @param [ActiveModel::Serializer::Reflection] reflection
+        # @return [void]
+        #
+        # @api private
+        #
+        def associate(reflection)
+          key = reflection.options[:key]
+          key ? self._reflections[key] = reflection : self._reflections[reflection.name] = reflection
+        end
+      end
+
+      # @param [JSONAPI::IncludeDirective] include_directive (defaults to the
+      #   +default_include_directive+ config value when not provided)
+      # @return [Enumerator<Association>]
+      #
+      def associations(include_directive = ActiveModelSerializers.default_include_directive)
+        return unless object
+
+        Enumerator.new do |y|
+          self.class._reflections.values.each do |reflection|
+            next if reflection.excluded?(self)
+            key = reflection.options.fetch(:key, reflection.name)
+            next unless include_directive.key?(key)
+            y.yield reflection.build_association(self, instance_options)
+          end
+        end
+      end
+    end
+  end
+end