gistfile1.rbx

require 'rubygems'
require 'test/unit'
require 'active_record'

module DefaultValuePlugin

class NormalValueContainer
	def initialize(value)
		@value = value
	end
	
	def evaluate
		return @value
	end
end

class BlockValueContainer
	def initialize(model_object, block)
		@model_object = self
		@block = block
	end
	
	def evaluate
		return @block.call(@model_object)
	end
end

module ClassMethods
	def default_value_for(attribute, value = nil, &block)
		if !method_defined?(:initialize_with_defaults)
			include(InstanceMethods)
			alias_method_chain :initialize, :defaults
			class_inheritable_accessor :_default_attribute_values
			self._default_attribute_values = {}
		end
		if block_given?
			container = BlockValueContainer.new(self, block)
		else
			container = NormalValueContainer.new(value)
		end
		_default_attribute_values[attribute.to_s] = container
	end
end

module InstanceMethods
	def initialize_with_defaults(attrs = nil)
		initialize_without_defaults(attrs) do
			self.class._default_attribute_values.each_pair do |attribute, container|
				if attrs.nil? || !attrs.keys.map(&:to_s).include?(attribute)
					__send__("#{attribute}=", container.evaluate)
				end
			end
			yield(self) if block_given?
		end
	end
end

end

ActiveRecord::Base.extend(DefaultValuePlugin::ClassMethods)
ActiveRecord::Base.establish_connection(
	:adapter => 'sqlite3',
	:database => 'test.sqlite3'
)
ActiveRecord::Base.connection.create_table(:numbers, :force => true) do |t|
	t.string :type
	t.integer :number
	t.integer :count, :null => false, :default => 1
end
ActiveRecord::Base.connection.execute("INSERT INTO numbers (number) VALUES (9876)")

class MyTest < Test::Unit::TestCase
	def define_model_class(name = "TestClass", parent_class_name = "ActiveRecord::Base", &block)
		Object.send(:remove_const, name) rescue nil
		eval("class #{name} < #{parent_class_name}; end", TOPLEVEL_BINDING)
		klass = eval(name, TOPLEVEL_BINDING)
		klass.class_eval(&block) if block_given?
	end
	
	def test_default_value_can_be_passed_as_argument
		define_model_class do
			set_table_name 'numbers'
			default_value_for(:number, 1234)
		end
		object = TestClass.new
		assert_equal 1234, object.number
	end
	
	def test_default_value_can_be_passed_as_block
		define_model_class do
			set_table_name 'numbers'
			default_value_for(:number) { 1234 }
		end
		object = TestClass.new
		assert_equal 1234, object.number
	end
	
	def test_overwrites_db_default
		define_model_class do
			set_table_name 'numbers'
			default_value_for :count, 1234
		end
		object = TestClass.new
		assert_equal 1234, object.count
	end
	
	def test_doesnt_overwrite_values_provided_by_mass_assignment
		define_model_class do
			set_table_name 'numbers'
			default_value_for :number, 1234
		end
		object = TestClass.new(:number => 1, :count => 2)
		assert_equal 1, object.number
	end
	
	def test_doesnt_overwrite_values_provided_by_constructor_block
		define_model_class do
			set_table_name 'numbers'
			default_value_for :number, 1234
		end
		object = TestClass.new do |x|
			x.number = 1
			x.count = 2
		end
		assert_equal 1, object.number
	end
	
	def test_doesnt_overwrite_explicitly_provided_nil_values_in_mass_assignment
		define_model_class do
			set_table_name 'numbers'
			default_value_for :number, 1234
		end
		object = TestClass.new(:number => nil)
		assert_nil object.number
	end
	
	def test_default_values_are_inherited
		define_model_class("TestSuperClass") do
			set_table_name 'numbers'
			default_value_for :number, 1234
		end
		define_model_class("TestClass", "TestSuperClass")
		object = TestClass.new
		assert_equal 1234, object.number
	end
	
	def test_doesnt_set_default_on_saved_records
		define_model_class do
			set_table_name 'numbers'
			default_value_for :number, 1234
		end
		assert_equal 9876, TestClass.find(:first).number
	end
end