Add simple attribute implementation backed by ivars

activemodel/lib/active_model.rb

@@ -26,6 +26,7 @@ $:.unshift(activesupport_path) if File.directory?(activesupport_path)
 require 'active_support'
 
 module ActiveModel
+  autoload :Attributes, 'active_model/attributes'
   autoload :Base, 'active_model/base'
   autoload :DeprecatedErrorMethods, 'active_model/deprecated_error_methods'
   autoload :Errors, 'active_model/errors'

activemodel/lib/active_model/attributes.rb

@@ -0,0 +1,17 @@
+require 'active_support/core_ext/object/instance_variables'
+
+module ActiveModel
+  module Attributes
+    def attributes
+      instance_values
+    end
+
+    def read_attribute(attr_name)
+      instance_variable_get(:"@#{attr_name}")
+    end
+
+    def write_attribute(attr_name, value)
+      instance_variable_set(:"@#{attr_name}", value)
+    end
+  end
+end

activemodel/test/cases/attributes_test.rb

@@ -0,0 +1,30 @@
+require 'cases/helper'
+
+class AttributesTest < ActiveModel::TestCase
+  class Person
+    include ActiveModel::Attributes
+    attr_accessor :name
+  end
+
+  test "reads attribute" do
+    p = Person.new
+    assert_equal nil, p.read_attribute(:name)
+
+    p.name = "Josh"
+    assert_equal "Josh", p.read_attribute(:name)
+  end
+
+  test "writes attribute" do
+    p = Person.new
+    assert_equal nil, p.name
+
+    p.write_attribute(:name, "Josh")
+    assert_equal "Josh", p.name
+  end
+
+  test "returns all attributes" do
+    p = Person.new
+    p.name = "Josh"
+    assert_equal({"name" => "Josh"}, p.attributes)
+  end
+end