activerecord after_set callback

after_set.rb

require "rubygems"
require "acts_as_fu"
require "test/unit"
include ActsAsFu

class ActiveRecord::Base
  def self.after_set(attribute, callback)
    after_save callback, :if => "#{attribute}_set?"

    class_eval <<-END
      def #{attribute}_set?
        @#{attribute}_set
      end

      def #{attribute}=(val)
        @#{attribute}_set = #{attribute}.blank? && val.present?
        super(val)
      end
    END
  end
end

class AfterSetTest < Test::Unit::TestCase
  def setup
    $CALLS = 0

    build_model :users do
      string :name
      string :status, :default => "OK"

      after_set :name, :some_callback

      validates_presence_of :status

      def some_callback
        $CALLS += 1
      end
    end
  end

  def test_it_triggers_callback_when_set
    user = User.new
    user.save!
    assert_equal 0, $CALLS

    user.name = "Pat"
    assert_equal 0, $CALLS # Does not get set until record saved

    user.save!
    assert_equal 1, $CALLS
  end

  def test_does_not_trigger_when_already_set
    user = User.new(:name => "Pat")
    user.save!

    $CALLS = 0 # Reset this to make sure we don't call it again

    user.name = "Neil"
    user.save!

    assert_equal 0, $CALLS
  end

  def test_does_not_trigger_when_set_to_nil
    user = User.new
    user.save!

    user.name = nil
    user.save!

    assert_equal 0, $CALLS
  end

  def test_does_not_trigger_when_record_invalid
    user = User.new(:status => nil)
    user.name = "Pat"
    assert ! user.valid?
    assert ! user.save
    assert_equal 0, $CALLS
  end

  def test_works_with_two_callbacks
    User.class_eval do
      after_set :name, :another_callback

      def another_callback
        $CALLS += 1
      end
    end

    user = User.create
    assert_equal 0, $CALLS

    user.name = "Pat"
    assert_equal 0, $CALLS # Does not get set until record saved

    user.save!
    assert_equal 2, $CALLS
  end
end