diff --git a/CHANGELOG.md b/CHANGELOG.md
index b6a852b06..ab451b60c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,14 +1,19 @@
 ## 0.10.x
 
 Breaking changes:
+
 Features:
+- [#1504](https://github.com/rails-api/active_model_serializers/pull/1504) Adds the changes missing from #1454
+  and add more tests for resource identifier and relationship objects. (@groyoh)
 - [#1018](https://github.com/rails-api/active_model_serializers/pull/1018) Add more tests and docs for top-level links. (@leandrocp)
 - [#1454](https://github.com/rails-api/active_model_serializers/pull/1454) Add support for
   relationship-level links and meta attributes. (@beauby)
 - [#1340](https://github.com/rails-api/active_model_serializers/pull/1340) Add support for resource-level meta. (@beauby)
+
 Fixes:
 - [#1501](https://github.com/rails-api/active_model_serializers/pull/1501) Adds tests for SerializableResource::use_adapter?,doc typos (@domitian)
 - [#1488](https://github.com/rails-api/active_model_serializers/pull/1488) Require ActiveSupport's string inflections (@nate00)
+
 Misc:
 
 ### v0.10.0.rc4 (2016/01/27 11:00 +00:00)
diff --git a/lib/active_model/serializer/adapter/json_api.rb b/lib/active_model/serializer/adapter/json_api.rb
index a41571933..cfe4e04dc 100644
--- a/lib/active_model/serializer/adapter/json_api.rb
+++ b/lib/active_model/serializer/adapter/json_api.rb
@@ -6,10 +6,9 @@ class JsonApi < Base
         autoload :PaginationLinks
         autoload :FragmentCache
         autoload :Link
-        autoload :Association
-        autoload :ResourceIdentifier
         autoload :Meta
         autoload :Deserialization
+        require 'active_model/serializer/adapter/json_api/api_objects'
 
         # TODO: if we like this abstraction and other API objects to it,
         # then extract to its own file and require it.
@@ -100,7 +99,7 @@ def resource_objects_for(serializers)
         end
 
         def process_resource(serializer, primary)
-          resource_identifier = JsonApi::ResourceIdentifier.new(serializer).as_json
+          resource_identifier = ApiObjects::ResourceIdentifier.new(serializer).as_json
           return false unless @resource_identifiers.add?(resource_identifier)
 
           resource_object = resource_object_for(serializer)
@@ -136,7 +135,7 @@ def attributes_for(serializer, fields)
 
         def resource_object_for(serializer)
           resource_object = cache_check(serializer) do
-            resource_object = JsonApi::ResourceIdentifier.new(serializer).as_json
+            resource_object = ApiObjects::ResourceIdentifier.new(serializer).as_json
 
             requested_fields = fieldset && fieldset.fields_for(resource_object[:type])
             attributes = attributes_for(serializer, requested_fields)
@@ -160,12 +159,13 @@ def resource_object_for(serializer)
         def relationships_for(serializer, requested_associations)
           include_tree = IncludeTree.from_include_args(requested_associations)
           serializer.associations(include_tree).each_with_object({}) do |association, hash|
-            hash[association.key] = JsonApi::Association.new(serializer,
+            hash[association.key] = ApiObjects::Relationship.new(
+              serializer,
               association.serializer,
               association.options,
               association.links,
-              association.meta)
-                                    .as_json
+              association.meta
+            ).as_json
           end
         end
 
diff --git a/lib/active_model/serializer/adapter/json_api/api_objects.rb b/lib/active_model/serializer/adapter/json_api/api_objects.rb
new file mode 100644
index 000000000..bad3173c3
--- /dev/null
+++ b/lib/active_model/serializer/adapter/json_api/api_objects.rb
@@ -0,0 +1,13 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          extend ActiveSupport::Autoload
+          autoload :Relationship
+          autoload :ResourceIdentifier
+        end
+      end
+    end
+  end
+end
diff --git a/lib/active_model/serializer/adapter/json_api/api_objects/relationship.rb b/lib/active_model/serializer/adapter/json_api/api_objects/relationship.rb
new file mode 100644
index 000000000..d1ebc1b96
--- /dev/null
+++ b/lib/active_model/serializer/adapter/json_api/api_objects/relationship.rb
@@ -0,0 +1,52 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class Relationship
+            def initialize(parent_serializer, serializer, options = {}, links = {}, meta = nil)
+              @object = parent_serializer.object
+              @scope = parent_serializer.scope
+
+              @options = options
+              @data = data_for(serializer, options)
+              @links = links.each_with_object({}) do |(key, value), hash|
+                hash[key] = Link.new(parent_serializer, value).as_json
+              end
+              @meta = meta.respond_to?(:call) ? parent_serializer.instance_eval(&meta) : meta
+            end
+
+            def as_json
+              hash = {}
+              hash[:data] = data if options[:include_data]
+              links = self.links
+              hash[:links] = links if links.any?
+              meta = self.meta
+              hash[:meta] = meta if meta
+
+              hash
+            end
+
+            protected
+
+            attr_reader :object, :scope, :data, :options, :links, :meta
+
+            private
+
+            def data_for(serializer, options)
+              if serializer.respond_to?(:each)
+                serializer.map { |s| ResourceIdentifier.new(s).as_json }
+              else
+                if options[:virtual_value]
+                  options[:virtual_value]
+                elsif serializer && serializer.object
+                  ResourceIdentifier.new(serializer).as_json
+                end
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/active_model/serializer/adapter/json_api/api_objects/resource_identifier.rb b/lib/active_model/serializer/adapter/json_api/api_objects/resource_identifier.rb
new file mode 100644
index 000000000..058f06031
--- /dev/null
+++ b/lib/active_model/serializer/adapter/json_api/api_objects/resource_identifier.rb
@@ -0,0 +1,39 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class ResourceIdentifier
+            def initialize(serializer)
+              @id = id_for(serializer)
+              @type = type_for(serializer)
+            end
+
+            def as_json
+              { id: id, type: type }
+            end
+
+            protected
+
+            attr_reader :id, :type
+
+            private
+
+            def type_for(serializer)
+              return serializer._type if serializer._type
+              if ActiveModelSerializers.config.jsonapi_resource_type == :singular
+                serializer.object.class.model_name.singular
+              else
+                serializer.object.class.model_name.plural
+              end
+            end
+
+            def id_for(serializer)
+              serializer.read_attribute_for_serialization(:id).to_s
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/active_model/serializer/adapter/json_api/association.rb b/lib/active_model/serializer/adapter/json_api/association.rb
deleted file mode 100644
index b6cfc70dd..000000000
--- a/lib/active_model/serializer/adapter/json_api/association.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Adapter
-      class JsonApi
-        class Association
-          def initialize(parent_serializer, serializer, options, links, meta)
-            @object = parent_serializer.object
-            @scope = parent_serializer.scope
-
-            @options = options
-            @data = data_for(serializer, options)
-            @links = links
-                     .map { |key, value| { key => Link.new(parent_serializer, value).as_json } }
-                     .reduce({}, :merge)
-            @meta = meta.respond_to?(:call) ? parent_serializer.instance_eval(&meta) : meta
-          end
-
-          def as_json
-            hash = {}
-            hash[:data] = @data if @options[:include_data]
-            hash[:links] = @links if @links.any?
-            hash[:meta] = @meta if @meta
-
-            hash
-          end
-
-          protected
-
-          attr_reader :object, :scope
-
-          private
-
-          def data_for(serializer, options)
-            if serializer.respond_to?(:each)
-              serializer.map { |s| ResourceIdentifier.new(s).as_json }
-            else
-              if options[:virtual_value]
-                options[:virtual_value]
-              elsif serializer && serializer.object
-                ResourceIdentifier.new(serializer).as_json
-              end
-            end
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/active_model/serializer/adapter/json_api/resource_identifier.rb b/lib/active_model/serializer/adapter/json_api/resource_identifier.rb
deleted file mode 100644
index 99bff2981..000000000
--- a/lib/active_model/serializer/adapter/json_api/resource_identifier.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Adapter
-      class JsonApi
-        class ResourceIdentifier
-          def initialize(serializer)
-            @id = id_for(serializer)
-            @type = type_for(serializer)
-          end
-
-          def as_json
-            { id: @id.to_s, type: @type }
-          end
-
-          protected
-
-          attr_reader :object, :scope
-
-          private
-
-          def type_for(serializer)
-            return serializer._type if serializer._type
-            if ActiveModelSerializers.config.jsonapi_resource_type == :singular
-              serializer.object.class.model_name.singular
-            else
-              serializer.object.class.model_name.plural
-            end
-          end
-
-          def id_for(serializer)
-            if serializer.respond_to?(:id)
-              serializer.id
-            else
-              serializer.object.id
-            end
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/active_model/serializer/reflection.rb b/lib/active_model/serializer/reflection.rb
index 89fa4074f..d7378e60f 100644
--- a/lib/active_model/serializer/reflection.rb
+++ b/lib/active_model/serializer/reflection.rb
@@ -42,17 +42,17 @@ def initialize(*)
 
       def link(name, value = nil, &block)
         @_links[name] = block || value
-        nil
+        :nil
       end
 
       def meta(value = nil, &block)
         @_meta = block || value
-        nil
+        :nil
       end
 
       def include_data(value = true)
         @_include_data = value
-        nil
+        :nil
       end
 
       def value(serializer)
@@ -60,7 +60,12 @@ def value(serializer)
         @scope = serializer.scope
 
         if block
-          instance_eval(&block)
+          block_value = instance_eval(&block)
+          if block_value == :nil
+            serializer.read_attribute_for_serialization(name)
+          else
+            block_value
+          end
         else
           serializer.read_attribute_for_serialization(name)
         end
diff --git a/test/adapter/json_api/api_objects/relationship_test.rb b/test/adapter/json_api/api_objects/relationship_test.rb
new file mode 100644
index 000000000..5564400ea
--- /dev/null
+++ b/test/adapter/json_api/api_objects/relationship_test.rb
@@ -0,0 +1,168 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class RelationshipTest < ActiveSupport::TestCase
+            def setup
+              @blog = Blog.new(id: 1)
+              @author = Author.new(id: 1, name: 'Steve K.', blog: @blog)
+              @serializer = BlogSerializer.new(@blog)
+              ActionController::Base.cache_store.clear
+            end
+
+            def test_relationship_with_data
+              expected = {
+                data: {
+                  id: '1',
+                  type: 'blogs'
+                }
+              }
+              test_relationship(expected, options: { include_data: true })
+            end
+
+            def test_relationship_with_nil_model
+              @serializer = BlogSerializer.new(nil)
+              expected = { data: nil }
+              test_relationship(expected, options: { include_data: true })
+            end
+
+            def test_relationship_with_nil_serializer
+              @serializer = nil
+              expected = { data: nil }
+              test_relationship(expected, options: { include_data: true })
+            end
+
+            def test_relationship_with_data_array
+              posts = [Post.new(id: 1), Post.new(id: 2)]
+              @serializer = ActiveModel::Serializer::ArraySerializer.new(posts)
+              @author.posts = posts
+              @author.blog = nil
+              expected = {
+                data: [
+                  {
+                    id: '1',
+                    type: 'posts'
+                  },
+                  {
+                    id: '2',
+                    type: 'posts'
+                  }
+                ]
+              }
+              test_relationship(expected, options: { include_data: true })
+            end
+
+            def test_relationship_data_not_included
+              test_relationship({}, options: { include_data: false })
+            end
+
+            def test_relationship_simple_link
+              links = { self: 'a link' }
+              test_relationship({ links: { self: 'a link' } }, links: links)
+            end
+
+            def test_relationship_many_links
+              links = {
+                self: 'a link',
+                related: 'another link'
+              }
+              expected = {
+                links: {
+                  self: 'a link',
+                  related: 'another link'
+                }
+              }
+              test_relationship(expected, links: links)
+            end
+
+            def test_relationship_block_link
+              links = { self: proc { "#{object.id}" } }
+              expected = { links: { self: "#{@blog.id}" } }
+              test_relationship(expected, links: links)
+            end
+
+            def test_relationship_block_link_with_meta
+              links = {
+                self: proc do
+                  href "#{object.id}"
+                  meta(id: object.id)
+                end
+              }
+              expected = {
+                links: {
+                  self: {
+                    href: "#{@blog.id}",
+                    meta: { id: @blog.id }
+                  }
+                }
+              }
+              test_relationship(expected, links: links)
+            end
+
+            def test_relationship_simple_meta
+              meta = { id: '1' }
+              expected = { meta: meta }
+              test_relationship(expected, meta: meta)
+            end
+
+            def test_relationship_block_meta
+              meta =  proc do
+                { id: object.id }
+              end
+              expected = {
+                meta: {
+                  id: @blog.id
+                }
+              }
+              test_relationship(expected, meta: meta)
+            end
+
+            def test_relationship_with_everything
+              links = {
+                self: 'a link',
+                related: proc do
+                  href "#{object.id}"
+                  meta object.id
+                end
+
+              }
+              meta = proc do
+                { id: object.id }
+              end
+              expected = {
+                data: {
+                  id: '1',
+                  type: 'blogs'
+                },
+                links: {
+                  self: 'a link',
+                  related: {
+                    href: '1', meta: 1
+                  }
+                },
+                meta: {
+                  id: @blog.id
+                }
+              }
+              test_relationship(expected, meta: meta, options: { include_data: true }, links: links)
+            end
+
+            private
+
+            def test_relationship(expected, params = {})
+              options = params.fetch(:options, {})
+              links = params.fetch(:links, {})
+              meta = params[:meta]
+              parent_serializer = AuthorSerializer.new(@author)
+              relationship = Relationship.new(parent_serializer, @serializer, options, links, meta)
+              assert_equal(expected, relationship.as_json)
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/test/adapter/json_api/api_objects/resource_identifier_test.rb b/test/adapter/json_api/api_objects/resource_identifier_test.rb
new file mode 100644
index 000000000..a40f07071
--- /dev/null
+++ b/test/adapter/json_api/api_objects/resource_identifier_test.rb
@@ -0,0 +1,88 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class ResourceIdentifierTest < ActiveSupport::TestCase
+            class WithDefinedTypeSerializer < Serializer
+              type 'with_defined_type'
+            end
+
+            class WithDefinedIdSerializer < Serializer
+              def id
+                'special_id'
+              end
+            end
+
+            class FragmentedSerializer < Serializer; end
+
+            def setup
+              @model = Author.new(id: 1, name: 'Steve K.')
+              ActionController::Base.cache_store.clear
+            end
+
+            def test_defined_type
+              test_type(WithDefinedTypeSerializer, 'with_defined_type')
+            end
+
+            def test_singular_type
+              test_type_inflection(AuthorSerializer, 'author', :singular)
+            end
+
+            def test_plural_type
+              test_type_inflection(AuthorSerializer, 'authors', :plural)
+            end
+
+            def test_id_defined_on_object
+              test_id(AuthorSerializer, @model.id.to_s)
+            end
+
+            def test_id_defined_on_serializer
+              test_id(WithDefinedIdSerializer, 'special_id')
+            end
+
+            def test_id_defined_on_fragmented
+              FragmentedSerializer.fragmented(WithDefinedIdSerializer.new(@author))
+              test_id(FragmentedSerializer, 'special_id')
+            end
+
+            private
+
+            def test_type_inflection(serializer_class, expected_type, inflection)
+              original_inflection = ActiveModelSerializers.config.jsonapi_resource_type
+              ActiveModelSerializers.config.jsonapi_resource_type = inflection
+              test_type(serializer_class, expected_type)
+              ActiveModelSerializers.config.jsonapi_resource_type = original_inflection
+            end
+
+            def test_type(serializer_class, expected_type)
+              serializer = serializer_class.new(@model)
+              resource_identifier = ResourceIdentifier.new(serializer)
+              expected = {
+                id: @model.id.to_s,
+                type: expected_type
+              }
+
+              assert_equal(expected, resource_identifier.as_json)
+            end
+
+            def test_id(serializer_class, id)
+              serializer = serializer_class.new(@model)
+              resource_identifier = ResourceIdentifier.new(serializer)
+              inflection = ActiveModelSerializers.config.jsonapi_resource_type
+              type = @model.class.model_name.send(inflection)
+              expected = {
+                id: id,
+                type: type
+              }
+
+              assert_equal(expected, resource_identifier.as_json)
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/test/adapter/json_api/links_test.rb b/test/adapter/json_api/links_test.rb
index 81dde4a30..43e37dd7e 100644
--- a/test/adapter/json_api/links_test.rb
+++ b/test/adapter/json_api/links_test.rb
@@ -17,18 +17,6 @@ class LinkAuthorSerializer < ActiveModel::Serializer
             link :yet_another do
               "//example.com/resource/#{object.id}"
             end
-
-            has_many :posts do
-              link :self do
-                href '//example.com/link_author/relationships/posts'
-                meta stuff: 'value'
-              end
-              link :related do
-                href '//example.com/link_author/posts'
-                meta count: object.posts.count
-              end
-              include_data false
-            end
           end
 
           def setup
@@ -91,23 +79,6 @@ def test_resource_links
             }
             assert_equal(expected, hash[:data][:links])
           end
-
-          def test_relationship_links
-            hash = serializable(@author, adapter: :json_api).serializable_hash
-            expected = {
-              links: {
-                self: {
-                  href: '//example.com/link_author/relationships/posts',
-                  meta: { stuff: 'value' }
-                },
-                related: {
-                  href: '//example.com/link_author/posts',
-                  meta: { count: 1 }
-                }
-              }
-            }
-            assert_equal(expected, hash[:data][:relationships][:posts])
-          end
         end
       end
     end
diff --git a/test/adapter/json_api/relationship_test.rb b/test/adapter/json_api/relationship_test.rb
new file mode 100644
index 000000000..110fbec4d
--- /dev/null
+++ b/test/adapter/json_api/relationship_test.rb
@@ -0,0 +1,173 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        class RelationshipTest < ActiveSupport::TestCase
+          RelationshipAuthor = Class.new(::Model)
+          class RelationshipAuthorSerializer < ActiveModel::Serializer
+            has_one :bio do
+              link :self, '//example.com/link_author/relationships/bio'
+            end
+
+            has_one :profile do
+              link :related do
+                "//example.com/profiles/#{object.profile.id}"
+              end
+            end
+
+            has_many :locations do
+              link :related do
+                ids = object.locations.map!(&:id).join(',')
+                href "//example.com/locations/#{ids}"
+              end
+            end
+
+            has_many :posts do
+              link :related do
+                ids = object.posts.map!(&:id).join(',')
+                href "//example.com/posts/#{ids}"
+                meta ids: ids
+              end
+            end
+
+            has_many :roles do
+              meta count: object.posts.count
+            end
+
+            has_one :blog do
+              link :self, '//example.com/link_author/relationships/blog'
+              include_data false
+            end
+
+            belongs_to :reviewer do
+              meta name: 'Dan Brown'
+              include_data true
+            end
+
+            has_many :likes do
+              link :related do
+                ids = object.likes.map!(&:id).join(',')
+                href "//example.com/likes/#{ids}"
+                meta ids: ids
+              end
+              meta liked: object.likes.any?
+            end
+          end
+
+          def setup
+            @post = Post.new(id: 1337, comments: [], author: nil)
+            @blog = Blog.new(id: 1337, name: 'extra')
+            @bio = Bio.new(id: 1337)
+            @like = Like.new(id: 1337)
+            @role = Role.new(id: 1337)
+            @profile = Profile.new(id: 1337)
+            @location = Location.new(id: 1337)
+            @reviewer = Author.new(id: 1337)
+            @author = RelationshipAuthor.new(
+              id: 1337,
+              posts: [@post],
+              blog: @blog,
+              reviewer: @reviewer,
+              bio: @bio,
+              likes: [@like],
+              roles: [@role],
+              locations: [@location],
+              profile: @profile
+            )
+          end
+
+          def test_relationship_simple_link
+            hash = serializable(@author, adapter: :json_api).serializable_hash
+            expected = {
+              data: {
+                id: '1337',
+                type: 'bios'
+              },
+              links: {
+                self: '//example.com/link_author/relationships/bio'
+              }
+            }
+            assert_equal(expected, hash[:data][:relationships][:bio])
+          end
+
+          def test_relationship_block_link
+            hash = serializable(@author, adapter: :json_api).serializable_hash
+            expected = {
+              data: { id: '1337', type: 'profiles' },
+              links: { related: '//example.com/profiles/1337' }
+            }
+            assert_equal(expected, hash[:data][:relationships][:profile])
+          end
+
+          def test_relationship_block_link_href
+            hash = serializable(@author, adapter: :json_api).serializable_hash
+            expected = {
+              data: [{ id: '1337', type: 'locations' }],
+              links: {
+                related: { href: '//example.com/locations/1337' }
+              }
+            }
+            assert_equal(expected, hash[:data][:relationships][:locations])
+          end
+
+          def test_relationship_block_link_meta
+            hash = serializable(@author, adapter: :json_api).serializable_hash
+            expected = {
+              data: [{ id: '1337', type: 'posts' }],
+              links: {
+                related: {
+                  href: '//example.com/posts/1337',
+                  meta: { ids: '1337' }
+                }
+              }
+            }
+            assert_equal(expected, hash[:data][:relationships][:posts])
+          end
+
+          def test_relationship_meta
+            hash = serializable(@author, adapter: :json_api).serializable_hash
+            expected = {
+              data: [{ id: '1337', type: 'roles' }],
+              meta: { count: 1 }
+            }
+            assert_equal(expected, hash[:data][:relationships][:roles])
+          end
+
+          def test_relationship_not_including_data
+            hash = serializable(@author, adapter: :json_api).serializable_hash
+            expected = {
+              links: { self: '//example.com/link_author/relationships/blog' }
+            }
+            assert_equal(expected, hash[:data][:relationships][:blog])
+          end
+
+          def test_relationship_including_data_explicit
+            hash = serializable(@author, adapter: :json_api).serializable_hash
+            expected = {
+              data: { id: '1337', type: 'authors' },
+              meta: { name: 'Dan Brown' }
+            }
+            assert_equal(expected, hash[:data][:relationships][:reviewer])
+          end
+
+          def test_relationship_with_everything
+            hash = serializable(@author, adapter: :json_api).serializable_hash
+            expected = {
+              data: [{ id: '1337', type: 'likes' }],
+              links: {
+                related: {
+                  href: '//example.com/likes/1337',
+                  meta: { ids: '1337' }
+                }
+              },
+              meta: { liked: true }
+            }
+            assert_equal(expected, hash[:data][:relationships][:likes])
+          end
+        end
+      end
+    end
+  end
+end