Merge pull request #24 from Adman65/polymorphic-associations

Polymorphic associations

lib/active_model/serializer.rb

@@ -80,6 +80,10 @@ module ActiveModel
           options[:key] || name
         end
 
+        def polymorphic?
+          options[:polymorphic]
+        end
+
         protected
 
         def find_serializable(object, scope, context, options)
@@ -115,11 +119,34 @@ module ActiveModel
 
       class HasOne < Config #:nodoc:
         def serialize(object, scope, context, options)
+          if polymorphic?
+            if object
+              find_serializable(object, scope, context, options).as_json(:root => polymorphic_key(object))
+            else
+              {}
+            end
+          else
             { key => object && find_serializable(object, scope, context, options).as_json(:root => false) }
           end
+        end
+
 
         def serialize_ids(object, scope)
-          { key => object && object.read_attribute_for_serialization(:id) }
+          if polymorphic? && object
+            { 
+              polymorphic_key(object) => object.read_attribute_for_serialization(:id),
+            }
+          elsif polymorphic? && !object
+            { }
+          elsif object
+            { key => object.read_attribute_for_serialization(:id) }
+          else
+            { key => nil }
+          end
+        end
+
+        def polymorphic_key(object)
+          object.class.to_s.demodulize.underscore.to_sym 
         end
       end
     end

test/serializer_test.rb

@@ -652,6 +652,95 @@ class SerializerTest < ActiveModel::TestCase
     }, hash.as_json)
   end
 
+  class PolymorphicUser < User ; end
+
+  class PolymorphicUserSerializer < ActiveModel::Serializer
+    attributes :first_name, :last_name
+  end
+
+  def test_polymorphic_has_one
+    polymorphic_blog = Class.new do
+      attr_accessor :writer
+    end
+
+    polymorphic_serializer = Class.new(ActiveModel::Serializer) do
+      has_one :writer, :polymorphic => true
+    end
+
+    user = PolymorphicUser.new
+    blog = polymorphic_blog.new
+    blog.writer = user
+
+    serializer = polymorphic_serializer.new(blog, user)
+
+    assert_equal({
+      :polymorphic_user => {
+        :first_name => "Jose",
+        :last_name => "Valim"
+      }
+    }, serializer.as_json)
+  end
+
+  def test_polymorphic_has_one_with_nil
+    polymorphic_blog = Class.new do
+      attr_accessor :writer
+    end
+
+    polymorphic_serializer = Class.new(ActiveModel::Serializer) do
+      has_one :writer, :polymorphic => true
+    end
+
+    user = PolymorphicUser.new
+    blog = polymorphic_blog.new
+    blog.writer = nil
+
+    serializer = polymorphic_serializer.new(blog, user)
+
+    assert_equal({
+    }, serializer.as_json)
+  end
+
+  def test_polymorphic_has_one_with_ids
+    polymorphic_blog = Class.new do
+      attr_accessor :writer
+    end
+
+    polymorphic_serializer = Class.new(ActiveModel::Serializer) do
+      embed :ids
+      has_one :writer, :polymorphic => true
+    end
+
+    user = PolymorphicUser.new :id => 1
+    blog = polymorphic_blog.new
+    blog.writer = user
+
+    serializer = polymorphic_serializer.new(blog, user)
+
+    assert_equal({
+      :polymorphic_user => 1
+    }, serializer.as_json)
+  end
+
+  def test_polymorphic_has_one_id_with_nil
+    polymorphic_blog = Class.new do
+      attr_accessor :writer
+    end
+
+    polymorphic_serializer = Class.new(ActiveModel::Serializer) do
+      embed :ids
+      has_one :writer, :polymorphic => true
+    end
+
+    user = PolymorphicUser.new
+    blog = polymorphic_blog.new
+    blog.writer = nil
+
+    serializer = polymorphic_serializer.new(blog, user)
+
+    assert_equal({
+    }, serializer.as_json)
+  end
+
   def test_root_provided_in_options
     author_serializer = Class.new(ActiveModel::Serializer) do
       attributes :id, :name