Ruby proxy method

foo.rb

class Proxy
  def proxy(context, &blk)
    @context = context
    @blk = blk
  end

  def method_missing(method, *args, &blk)
    __object.send(method, *args, &blk)
  end

  def __object
    @object ||= @blk.call(@context)
  end
end

p = Proxy.new

p.proxy(self) {|context| context.to_s }
p + 'HelloWorld' # => 'mainHelloWorld'

factory :user do
  post Proxy.new.proxy(self) {|self| self.build :post }
end