serialize_ids call methods on the corresponding serializer if defined

lib/active_model/serializer.rb

@@ -382,12 +382,7 @@ module ActiveModel
       association = association_class.new(name, options, self.options)
 
       if association.embed_ids?
-        node[association.key] =
-          if options[:embed_key] || self.respond_to?(name) || !self.object.respond_to?(association.id_key)
-            association.serialize_ids
-          else
-            self.object.read_attribute_for_serialization(association.id_key)
-          end
+        node[association.key] = association.serialize_ids
 
         if association.embed_in_root? && hash.nil?
           raise IncludeError.new(self.class, association.name)

lib/active_model/serializer/associations.rb

@@ -34,7 +34,7 @@ module ActiveModel
         @embed_in_root = options[:include]
 
         serializer = options[:serializer]
-        @serializer = serializer.is_a?(String) ? serializer.constantize : serializer
+        @serializer_class = serializer.is_a?(String) ? serializer.constantize : serializer
 
         @options = options
         @serializer_options = serializer_options
@@ -59,11 +59,11 @@ module ActiveModel
 
       private
 
-      attr_reader :embed_key, :serializer, :options, :serializer_options
+      attr_reader :embed_key, :serializer_class, :options, :serializer_options
 
       def find_serializable(object)
-        if serializer
-          serializer.new(object, serializer_options)
+        if serializer_class
+          serializer_class.new(object, serializer_options)
         elsif object.respond_to?(:active_model_serializer) && (ams = object.active_model_serializer)
           ams.new(object, serializer_options)
         else
@@ -94,7 +94,12 @@ module ActiveModel
 
         def serialize_ids
           object.map do |item|
-            item.read_attribute_for_serialization(embed_key)
+            serializer = find_serializable(item)
+            if serializer.respond_to?(embed_key)
+              serializer.send(embed_key)
+            else
+              item.read_attribute_for_serialization(embed_key)
+            end
           end
         end
       end
@@ -143,7 +148,14 @@ module ActiveModel
 
         def serialize_ids
           if object
-            id = object.read_attribute_for_serialization(embed_key)
+            serializer = find_serializable(object)
+            id =
+              if serializer.respond_to?(embed_key)
+                serializer.send(embed_key)
+              else
+                object.read_attribute_for_serialization(embed_key)
+              end
+
             if polymorphic?
               {
                 :type => polymorphic_key,

test/serializer_test.rb

@@ -454,6 +454,39 @@ class SerializerTest < ActiveModel::TestCase
     }, json)
   end
 
+  def test_methods_take_priority_over_associations_and_call_the_appropriate_id_method
+    comment_serializer = Class.new(ActiveModel::Serializer) do
+      def id
+        "OMG"
+      end
+    end
+
+    post_serializer = Class.new(ActiveModel::Serializer) do
+      attributes :title
+      has_many :comments, :serializer => comment_serializer
+      embed :ids
+
+      def comments
+        object.comments[0,1]
+      end
+    end
+
+    post = Post.new(:title => "My Post")
+    comments = [Comment.new(:title => "Comment1", :id => 1), Comment.new(:title => "Comment2", :id => 2)]
+    post.comments = comments
+
+    post.class_eval do
+      define_method :comment_ids, lambda {
+        self.comments.map { |c| c.read_attribute_for_serialization(:id) }
+      }
+    end
+    json = post_serializer.new(post).as_json
+    assert_equal({
+      :title => "My Post",
+      :comment_ids => ["OMG"]
+    }, json)
+  end
+
   def test_embed_objects
     serializer = post_serializer
 
@@ -684,6 +717,42 @@ class SerializerTest < ActiveModel::TestCase
     }, hash.as_json)
   end
 
+  def test_embed_id_for_has_one_overriding_associated_id
+    author_serializer = Class.new(ActiveModel::Serializer) do
+      def id
+        "OMG"
+      end
+    end
+
+    serializer_class = Class.new(ActiveModel::Serializer) do
+      embed :ids
+      root :post
+
+      attributes :title, :body
+      has_one :author, :serializer => author_serializer
+    end
+
+    post_class = Class.new(Model) do
+      attr_accessor :author
+    end
+
+    author_class = Class.new(Model)
+
+    post = post_class.new(:title => "New Post", :body => "It's a new post!")
+    author = author_class.new(:id => 5)
+    post.author = author
+
+    hash = serializer_class.new(post)
+
+    assert_equal({
+      :post => {
+        :title => "New Post",
+        :body => "It's a new post!",
+        :author_id => "OMG"
+      }
+    }, hash.as_json)
+  end
+
   def test_embed_objects_for_has_one
     author_serializer = Class.new(ActiveModel::Serializer) do
       attributes :id, :name