3 files changed, 122 insertions, 0 deletions
diff --git a/activemodel/lib/active_model.rb b/activemodel/lib/active_model.rb
index d0e2a6f39c..28765b00bb 100644
--- a/activemodel/lib/active_model.rb
+++ b/activemodel/lib/active_model.rb
@@ -43,6 +43,7 @@ module ActiveModel
   autoload :Observer, 'active_model/observing'
   autoload :Observing
   autoload :SecurePassword
+  autoload :Serializer
   autoload :Serialization
   autoload :TestCase
   autoload :Translation
diff --git a/activemodel/lib/active_model/serializer.rb b/activemodel/lib/active_model/serializer.rb
new file mode 100644
index 0000000000..2eca3ebc5e
--- /dev/null
+++ b/activemodel/lib/active_model/serializer.rb
@@ -0,0 +1,46 @@
+require "active_support/core_ext/class/attribute"
+require "active_support/core_ext/string/inflections"
+require "set"
+
+module ActiveModel
+  class Serializer
+    class_attribute :_attributes
+    self._attributes = Set.new
+
+    def self.attributes(*attrs)
+      self._attributes += attrs
+    end
+
+    attr_reader :object, :scope
+
+    def self.inherited(klass)
+      name = klass.name.demodulize.underscore.sub(/_serializer$/, '')
+
+      klass.class_eval do
+        alias_method name.to_sym, :object
+      end
+    end
+
+    def initialize(object, scope)
+      @object, @scope = object, scope
+    end
+
+    def as_json(*)
+      serializable_hash
+    end
+
+    def serializable_hash(*)
+      attributes
+    end
+
+    def attributes
+      hash = {}
+
+      _attributes.each do |name|
+        hash[name] = @object.read_attribute_for_serialization(name)
+      end
+
+      hash
+    end
+  end
+end
diff --git a/activemodel/test/cases/serializer_test.rb b/activemodel/test/cases/serializer_test.rb
new file mode 100644
index 0000000000..91ed6987a1
--- /dev/null
+++ b/activemodel/test/cases/serializer_test.rb
@@ -0,0 +1,75 @@
+require "cases/helper"
+
+class SerializerTest < ActiveModel::TestCase
+  class User
+    attr_accessor :superuser
+
+    def super_user?
+      @superuser
+    end
+
+    def read_attribute_for_serialization(name)
+      hash = { :first_name => "Jose", :last_name => "Valim", :password => "oh noes yugive my password" }
+      hash[name]
+    end
+  end
+
+  class UserSerializer < ActiveModel::Serializer
+    attributes :first_name, :last_name
+  end
+
+  class User2Serializer < ActiveModel::Serializer
+    attributes :first_name, :last_name
+
+    def serializable_hash(*)
+      attributes.merge(:ok => true).merge(scope)
+    end
+  end
+
+  class MyUserSerializer < ActiveModel::Serializer
+    attributes :first_name, :last_name
+
+    def serializable_hash(*)
+      hash = attributes
+      hash = hash.merge(:super_user => true) if my_user.super_user?
+      hash
+    end
+  end
+
+  def test_attributes
+    user = User.new
+    user_serializer = UserSerializer.new(user, nil)
+
+    hash = user_serializer.as_json
+
+    assert_equal({ :first_name => "Jose", :last_name => "Valim" }, hash)
+  end
+
+  def test_attributes_method
+    user = User.new
+    user_serializer = User2Serializer.new(user, {})
+
+    hash = user_serializer.as_json
+
+    assert_equal({ :first_name => "Jose", :last_name => "Valim", :ok => true }, hash)
+  end
+
+  def test_serializer_receives_scope
+    user = User.new
+    user_serializer = User2Serializer.new(user, {:scope => true})
+
+    hash = user_serializer.as_json
+
+    assert_equal({ :first_name => "Jose", :last_name => "Valim", :ok => true, :scope => true }, hash)
+  end
+
+  def test_pretty_accessors
+    user = User.new
+    user.superuser = true
+    user_serializer = MyUserSerializer.new(user, nil)
+
+    hash = user_serializer.as_json
+
+    assert_equal({ :first_name => "Jose", :last_name => "Valim", :super_user => true }, hash)
+  end
+end