From: gotoken@... (GOTO Kentaro)
Date: 1999-05-23T12:23:16+09:00
Subject: [ruby-talk:00335] Re: module-class calling

Hi, 

In message "[ruby-talk:00334] Re: module-class calling"
    on 99/05/22, "Michael Neumann" <neumann@s-direktnet.de> writes:

>But now I have to declare also the functions, which are called by "hello" as
>module_functions.
>Following example does not work (without :bye):
>
> module A
>    def bye
>      print "BYE\n"
>    end
>
>    def hello
>      print "HELLO\n"
>      bye
>    end
>
>    module_function :hello   #, :bye
>  end
>
>  class B
>    def call_A
>      A.hello
>    end
>  end
>
>  x = B.new
>  x.call_A
>
>Is the only solution to declare all functions inside the module, which are
>called from a module-function ('hello'),
>as module_function (like 'bye'), even if they are not called from outside
>the module?

Well, the module-function are called only as either a singleton 
method of the module or an instance method after including the module. 
So, if you want call `hello' as a singleton method and `hello' calls
`bye' you have to put `module_function :bye'. 

By the way, I use modules when I want
  (1) to provide a name space for the constants, 
  (2) to let several classes include a same module, or 
  (3) to define many singleton methods as module_function

The case (2) is known as mixin.  You can see an example of the case (3) 
in the mathematical modules, e.g., lib/rational.rb etc. 

-- gotoken