Extract links and type-related methods to their own module.

lib/active_model/serializer/adapter/json_api.rb

@@ -208,7 +208,7 @@ module ActiveModel
         end
 
         def links_for(serializer)
-          serializer.links.each_with_object({}) do |(name, value), hash|
+          serializer._links.each_with_object({}) do |(name, value), hash|
             hash[name] =
               if value.respond_to?(:call)
                 link = Link.new(serializer)

lib/active_model/serializer/links.rb

@@ -0,0 +1,33 @@
+module ActiveModel
+  class Serializer
+    module Links
+      extend ActiveSupport::Concern
+
+      included do
+        with_options instance_writer: false, instance_reader: true do |serializer|
+          serializer.class_attribute :_links # @api private
+          self._links ||= {}
+        end
+
+        extend ActiveSupport::Autoload
+      end
+
+      module ClassMethods
+        def inherited(base)
+          super
+          base._links = _links.dup
+        end
+
+        # Define a link on a serializer.
+        # @example
+        #   link :self { "/posts/#{object.id}" }
+        # @example
+        #   link :self, "/user"
+        #
+        def link(name, value = nil, &block)
+          _links[name] = block || value
+        end
+      end
+    end
+  end
+end

lib/active_model/serializer/type.rb

@@ -0,0 +1,25 @@
+module ActiveModel
+  class Serializer
+    module Type
+      extend ActiveSupport::Concern
+
+      included do
+        with_options instance_writer: false, instance_reader: true do |serializer|
+          serializer.class_attribute :_type # @api private
+        end
+
+        extend ActiveSupport::Autoload
+      end
+
+      module ClassMethods
+        # Set the JSON API type of a serializer.
+        # @example
+        #   class AdminAuthorSerializer < ActiveModel::Serializer
+        #     type 'authors'
+        def type(type)
+          self._type = type
+        end
+      end
+    end
+  end
+end