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A Successful Attempt at Mangling Ruby

2009 February 5
by Nayan Hajratwala

I’m working on the Ruby Koans by Edgecase which has been a really nice way to introduce myself (again) to Ruby. It’s the right mix of hand-holding and “solve-it-yourself” problems.

I just finished the about_proxy_object_project.rb Koan, and while it works, I fear that I’ve fairly well mangled Ruby, and there are probably infinitely more elegant ways to do this. My code looks like Java transcribed into Ruby.

Anyway, here is the code. If you have some spare time, take a look and see what I could have done better. I wrote the Proxy class, the rest was supplied.

# Project: Create a Proxy Class
#
# In this assignment, create a proxy class (one is started for you
# below).  You should be able to initialize the proxy object with any
# object.  Any messages sent to the proxy object should be forwarded
# to the target object.  As each message is sent, the proxy should
# record the name of the method send.
#
# The proxy class is started for you.  You will need to add a method
# missing handler and any other supporting methods.  The specification
# of the Proxy class is given in the AboutProxyObjectProject koan.

class Proxy

  class MessageLog
    attr_accessor :message_name
    attr_accessor :count

    def initialize(message_name)
      @message_name = message_name
      @count = 1
    end

    def increment_count
      @count = @count + 1
    end

  end

  def initialize(target_object)
    @object = target_object
    @messages = []
  end

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

  def increment_message_count(message_name)
      message_log = called?(message_name)
      if message_log.nil?
        @messages < < MessageLog.new(message_name)
      else
        message_log.increment_count
      end
  end

  def messages
    @messages.collect { |message_log| message_log.message_name }
  end

  def called?(command)

    matched_message_log = nil

    @messages.each do |message_log|
      if message_log.message_name == command
        matched_message_log = message_log
      end
    end

    matched_message_log
  end

  def number_of_times_called(command)
    message_log = called?(command)

    message_log.nil? ? 0 : message_log.count
  end

end

# The proxy object should pass the following Koan:
#
class AboutProxyObjectProject < EdgeCase::Koan
  def test_proxy_method_returns_wrapped_object
    # NOTE: The Television class is defined below
    tv = Proxy.new(Television.new)

    assert tv.instance_of?(Proxy)
  end

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

    tv.channel = 10
    tv.power

    assert_equal 10, tv.channel
    assert tv.on?
  end

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

    tv.power
    tv.channel = 10

    assert_equal [:power, :channel=], tv.messages
  end

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

    assert_raise(NoMethodError) do
      tv.no_such_method
    end
  end

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

    tv.power
    tv.power

    assert tv.called?(:power)
    assert ! tv.called?(:channel)
  end

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

    tv.power
    tv.channel = 48
    tv.power

    assert_equal 2, tv.number_of_times_called(:power)
    assert_equal 1, tv.number_of_times_called(:channel=)
    assert_equal 0, tv.number_of_times_called(:on?)
  end

  def test_proxy_can_record_more_than_just_tv_objects
    proxy = Proxy.new("Code Mash 2009")

    proxy.upcase!
    result = proxy.split

    assert_equal ["CODE", "MASH", "2009"], result
    assert_equal [:upcase!, :split], proxy.messages
  end
end

# ====================================================================
# The following code is to support the testing of the Proxy class.  No
# changes should be necessary to anything below this comment.

# Example class using in the proxy testing above.
class Television
  attr_accessor :channel

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

  def on?
    @power == :on
  end
end

# Tests for the Television class.  All of theses tests should pass.
class TelevisionTest < EdgeCase::Koan
  def test_it_turns_on
    tv = Television.new

    tv.power
    assert tv.on?
  end

  def test_it_also_turns_off
    tv = Television.new

    tv.power
    tv.power

    assert ! tv.on?
  end

  def test_edge_case_on_off
    tv = Television.new

    tv.power
    tv.power
    tv.power

    assert tv.on?

    tv.power

    assert ! tv.on?
  end

  def test_can_set_the_channel
    tv = Television.new

    tv.channel = 11
    assert_equal 11, tv.channel
  end
end