From: Trans <transfire@...>
Date: 2007-09-09T17:53:48+09:00
Subject: Re: module_function :func vs. MyModule.func?



On Sep 8, 10:54 pm, 7stud -- <dol...@excite.com> wrote:
> The following produce the same output:
>
> module MyModule
>     def greet
>         puts "hello"
>     end
>
>     module_function :greet
> end
>
> MyModule.greet
>
> #-----vs.-----------
>
> module MyModule
>     def MyModule.greet
>         puts "hello"
>     end
> end
>
> MyModule.greet
>
> What is module_function used for?


Allow me to further confuse you:

  module MyModule
      extend self

      def greet
          puts "hello"
      end
  end

  MyModule.greet

Now I will explain. I the 1st case, using module_function makes an
actual copy of the instance method and defines it as a singleton
method of the module. In the 2nd case, you never have the instance
method to begin with, you simply defined the singleton method
directly. So to illustrate, the 1st example is equivalent to this:

  module MyModule
      def greet
          puts "hello"
      end

      def MyModule.greet
          puts "hello"
      end
  end

Now for my last example. In which case, we defined the instance
method, but have also included the module into it's own singleton
space. It is functionally the same as the 1st case but is also dynamic
--if we were to add a new method to MyModule later it would
automatically appear as a module method as well.

HTH,
T.