Ruby Koans 代理项目

Question

I'm walking through the Ruby Koans and I have a trouble in about_proxy_object_project.rb
This is my solution

class Proxy
  attr_reader :messages

  def initialize(target_object)
    @object = target_object
    # ADD MORE CODE HERE
    @messages = []
  end

  def number_of_times_called(method_name)
    @messages.count method_name
  end

  def called?(method_name)
    @messages.include? method_name
  end 

  def method_missing(method_name, *args, &block)
    if @object.respond_to? method_name  
      @object.send(method_name, *args)
      @messages << method_name
    else
      super method_name, *args, &block
    end
  end
end

but when I typed rake I got this

The answers you seek...
  Expected 10 to equal [:channel=, :power, :channel]

Please meditate on the following code:
  /home/Shanicky/koans/about_proxy_object_project.rb:61:in `test_tv_methods_still_perform_their_function'

and in my about_proxy_object_project.rb

def test_tv_methods_still_perform_their_function
  tv = Proxy.new(Television.new)

  tv.channel = 10
  tv.power

  assert_equal 10, tv.channel # this is the 61st line
  assert tv.on?
end 

I am confused
Where i did do wrong?
Thanks all

and this is my Television class

class Television
  attr_accessor :channel

  def power
    if @power == :on
      @power = :off
    else
      @power = :on
    end
  end

  def on?
    @power == :on
  end
end

Answer 1

In this if clause:

if @object.respond_to? method_name  
  @object.send(method_name, *args)
  @messages << method_name # <-- this is the return value you get
else
  super method_name, *args, &block
end

The check @object.respond_to? method_name @object.respond_to? method_name always evaluates to true because the Television class defines all these methods you've called on its objects ( channel= , power , channel ). Therefore the first branch of the if runs and this code essentially adds to the @messages instance variable (which is an Array ) the method names that you are calling.

So when you call tv.channel the return value of the method is that commented statement in the above code, which of course is not equal to 10 . You essentially get the return value of @messages << method_name which is the new @messages array, which actually contains all the undefined method you've called until that time: [:channel=, :power, :channel] .

Answer 2

You can just use 'send' without checking. There is no purpose of using 'else' because it always returns some Exception.

def method_missing(method_name, *args, &block)
  @messages << method_name
  @object.send(method_name, *args, &block)
end

Answer 3

if you swap the two statements: @object.send(method_name, *args) @messages << method_name # <-- this is the return value you get

so: @messages << method_name # <-- this is the return value you get @object.send(method_name, *args)

then the return value would be whatever is returned by the method_name, and so in the case of tv.channel it would return 10 as expected in your test.

I think this is just saying the same thing as in the answer, but thought it worth making it clearer