Serialize just attributes

lib/active_model/serializer.rb

@@ -0,0 +1,43 @@
+module ActiveModel
+  class Serializer
+    class << self
+      def inherited(base)
+        base._attributes = {}
+      end
+
+      attr_accessor :_attributes
+
+      def attributes(*attrs)
+        @_attributes = attrs.map(&:to_s)
+
+        attrs.each do |attr|
+          define_method attr do
+            object.read_attribute_for_serialization(attr)
+          end
+        end
+      end
+    end
+
+    def initialize(object)
+      @object = object
+    end
+    attr_accessor :object
+
+    alias read_attribute_for_serialization send
+
+    def attributes
+      self.class._attributes.each_with_object({}) do |name, hash|
+        hash[name] = send(name)
+      end
+    end
+
+    def serializable_hash(options={})
+      return nil if object.nil?
+      attributes
+    end
+
+    def as_json(options={})
+      serializable_hash
+    end
+  end
+end

test/serializer/attributes_test.rb

@@ -0,0 +1,44 @@
+require 'newbase/test_helper'
+require 'newbase/active_model/serializer'
+
+module SerializerTest
+  module Attributes
+    class Model
+      def initialize(hash={})
+        @attributes = hash
+      end
+
+      def read_attribute_for_serialization(name)
+        @attributes[name]
+      end
+    end
+
+    class ModelSerializer < ActiveModel::Serializer
+      attributes :attr1, :attr2
+    end
+
+    class Test < ActiveModel::TestCase
+      def setup
+        model = Model.new({ :attr1 => 'value1', :attr2 => 'value2', :attr3 => 'value3' })
+        @model_serializer = ModelSerializer.new(model)
+      end
+
+      def test_attributes_definition
+        assert_equal(['attr1', 'attr2'],
+                     @model_serializer.class._attributes)
+      end
+
+      def test_attributes_serialization_using_serializable_hash
+        assert_equal({
+          'attr1' => 'value1', 'attr2' => 'value2'
+        }, @model_serializer.serializable_hash)
+      end
+
+      def test_attributes_serialization_using_as_json
+        assert_equal({
+          'attr1' => 'value1', 'attr2' => 'value2'
+        }, @model_serializer.as_json)
+      end
+    end
+  end
+end

test/test_helper.rb

@@ -0,0 +1,5 @@
+ENV['RAILS_ENV'] = 'test'
+
+require 'bundler/setup'
+require 'rails'
+require 'rails/test_help'