Add association_ids

activemodel/lib/active_model/serializer.rb

@@ -18,12 +18,25 @@ def serialize(collection, scope)
             serializer.new(item, scope).serializable_hash
           end
         end
+
+        def serialize_ids(collection, scope)
+          # use named scopes if they are present
+          return collection.ids if collection.respond_to?(:ids)
+
+          collection.map do |item|
+            item.read_attribute_for_serialization(:id)
+          end
+        end
       end
 
       class HasOne < Config
         def serialize(object, scope)
           serializer.new(object, scope).serializable_hash
         end
+
+        def serialize_ids(object, scope)
+          object.read_attribute_for_serialization(:id)
+        end
       end
     end
 
@@ -80,7 +93,11 @@ def as_json(*)
     end
 
     def serializable_hash
-      hash = attributes
+      attributes.merge(associations)
+    end
+
+    def associations
+      hash = {}
 
       _associations.each do |association|
         associated_object = send(association.name)
@@ -90,6 +107,17 @@ def serializable_hash
       hash
     end
 
+    def association_ids
+      hash = {}
+
+      _associations.each do |association|
+        associated_object = send(association.name)
+        hash[association.name] = association.serialize_ids(associated_object, scope)
+      end
+
+      hash
+    end
+
     def attributes
       hash = {}
 

activemodel/test/cases/serializer_test.rb

@@ -182,11 +182,12 @@ def test_overridden_associations
 
     blog_serializer = Class.new(ActiveModel::Serializer) do
       const_set(:PersonSerializer, author_serializer)
-      has_one :person
 
       def person
         object.author
       end
+
+      has_one :person
     end
 
     user = User.new
@@ -200,4 +201,62 @@ def person
       }
     }, json)
   end
+
+  def post_serializer(type)
+    Class.new(ActiveModel::Serializer) do
+      attributes :title, :body
+      has_many :comments, :serializer => CommentSerializer
+
+      define_method :serializable_hash do
+        post_hash = attributes
+        post_hash.merge!(send(type))
+        post_hash
+      end
+    end
+  end
+
+  def test_associations
+    post = Post.new(:title => "New Post", :body => "Body of new post", :email => "tenderlove@tenderlove.com")
+    comments = [Comment.new(:title => "Comment1"), Comment.new(:title => "Comment2")]
+    post.comments = comments
+
+    serializer = post_serializer(:associations).new(post, nil)
+
+    assert_equal({
+      :title => "New Post",
+      :body => "Body of new post",
+      :comments => [
+        { :title => "Comment1" },
+        { :title => "Comment2" }
+      ]
+    }, serializer.as_json)
+  end
+
+  def test_association_ids
+    serializer = post_serializer(:association_ids)
+
+    serializer.class_eval do
+      def as_json(*)
+        { post: serializable_hash }.merge(associations)
+      end
+    end
+
+    post = Post.new(:title => "New Post", :body => "Body of new post", :email => "tenderlove@tenderlove.com")
+    comments = [Comment.new(:title => "Comment1", :id => 1), Comment.new(:title => "Comment2", :id => 2)]
+    post.comments = comments
+
+    serializer = serializer.new(post, nil)
+
+    assert_equal({
+      :post => {
+        :title => "New Post",
+        :body => "Body of new post",
+        :comments => [1, 2]
+      },
+      :comments => [
+        { :title => "Comment1" },
+        { :title => "Comment2" }
+      ]
+    }, serializer.as_json)
+  end
 end