start implementing json_api adapter to understand how associations should work

lib/active_model/serializer/adapter.rb

@@ -4,6 +4,7 @@ module ActiveModel
       extend ActiveSupport::Autoload
       autoload :SimpleAdapter
       autoload :NullAdapter
+      autoload :JsonApiAdapter
 
       attr_reader :serializer
 

lib/active_model/serializer/adapter/json_api_adapter.rb

@@ -0,0 +1,24 @@
+module ActiveModel
+  class Serializer
+    class Adapter
+      class JsonApiAdapter < Adapter
+        def serializable_hash(options = {})
+          hash = serializer.attributes.each_with_object({}) do |(attr, value), h|
+            h[attr] = value
+          end
+
+          serializer.associations(only: [:id]).each_with_object({}) do |(attr, value), h|
+            case value
+            when ActiveModel::Serializer::ArraySerializer
+              # process has_many association
+            when ActiveModel::Serializer
+              # process belongs_to association
+            else
+              # what?
+            end
+          end
+        end
+      end
+    end
+  end
+end

test/adapter/json_api_adapter_test.rb

@@ -0,0 +1,31 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class Adapter
+      class JsonApiTest < Minitest::Test
+        def setup
+          @post = ::Model.new(title: 'New Post', body: 'Body')
+          @first_comment = ::Model.new(id: 1, body: 'ZOMG A COMMENT')
+          @second_comment = ::Model.new(id: 2, body: 'ZOMG ANOTHER COMMENT')
+          @post.comments = [@first_comment, @second_comment]
+          @first_comment.post = @post
+          @second_comment.post = @post
+
+          @post_serializer_class = def_serializer do
+            attributes :title, :body
+            has_many :comments
+          end
+
+          @post_serializer = @post_serializer_class.new(@post)
+          @adapter = ActiveModel::Serializer::Adapter::JsonApiAdapter.new(@post_serializer)
+        end
+
+        def test_includes_comment_ids
+          assert_equal(['1', '2'], @adapter.serializable_hash[:comments])
+        end
+      end
+    end
+  end
+end
+

test/fixtures/poro.rb

@@ -10,6 +10,16 @@ class Model
       @attributes[name]
     end
   end
+
+  def method_missing(meth, *args)
+    if meth.to_s =~ /^(.*)=$/
+      @attributes[$1.to_sym] = args[0]
+    elsif @attributes.key?(meth)
+      @attributes[meth]
+    else
+      super
+    end
+  end
 end
 
 class Profile < Model

test/test_helper.rb

@@ -25,3 +25,7 @@ ActionController::TestCase.class_eval do
     @routes = TestHelper::Routes
   end
 end
+
+def def_serializer(&block)
+  Class.new(ActiveModel::Serializer, &block)
+end