Ruby proxy pattern

proxy_test.rb

class ProxyTest

  attr_accessor :scope

  class ScopeProxy

    def initialize(obj, scope)
      @obj = obj
      @scope = scope
    end

    def method_missing(method, *args, &block)
      if @obj.respond_to?(method)
        with_scope do
          @obj.send(method)
        end
      else
        super
      end
    end

  private

    def with_scope(&block)
      @prev_scope = @obj.scope
      @obj.scope = @scope
      value = block.call
      @obj.scope = @prev_scope
      value
    end

  end

  def doubled
    ScopeProxy.new(self, :double)
  end

  def tripled
    ScopeProxy.new(self, :tripled)
  end

  def value
    case @scope
    when :tripled; 3
    when :double;  2
    else           1
    end
  end

end

test = ProxyTest.new
puts test.value # 1 
puts test.doubled.value # 2
puts test.tripled.value # 3
puts test.value # 1