instance_eval_example.rb

class Controller
  attr_reader :tag

  def initialize
    @tag = "Controller"
    @window = Window.new(self)
    @window.show
    hello
    hello_again
  end
end

class Window
  attr_reader :tag

  def initialize(controller)
    @controller = controller
  end

  def show
    @tag = "World"

    @controller.instance_eval do
      def hello
        puts "Hello #{tag}!"   # => Hello Controller!
      end
    end
    #
    # Perform outer self discovery within the instance method since
    # evaluating strings is not supported in RubyMotion (RuntimeError)
    #
    @controller.instance_eval do
      def hello_again
        control = instance_variables.find do |var|
          klass = instance_variable_get(var)
          klass.is_a?(Window) && klass.instance_variable_get("@controller") == self
        end
        puts "Hello #{instance_variable_get(control).tag}!"   # => Hello World!
      end
    end

    # # Find controller's instance variable that is current self.
    # window = @controller.instance_variables.find { |var| @controller.instance_variable_get(var) == self }
    # 
    # # Now we can use the outer self within the instance_eval.
    # @controller.instance_eval(%Q/
    #   def hello_again
    #     tag = #{window}.tag
    #     puts "Hello #{tag}!"   # => Hello World!
    #   end
    # /)
  end
end

Controller.new