From: Mark Hubbart <discord@...>
Date: 2004-04-24T03:50:31+09:00
Subject: Re: Modules & include


On Apr 23, 2004, at 11:34 AM, Andreas Schwarz wrote:

> Why do I get an exception? Shouldn't Mod2 have the method return_true
> because it included Mod1?
>
> irb(main):001:0> module Mod1
> irb(main):002:1>   def return_true
> irb(main):003:2>     true
> irb(main):004:2>   end
> irb(main):005:1> end
> => nil
> irb(main):006:0> module Mod2
> irb(main):007:1>   include Mod1
> irb(main):008:1>   def self.test
> irb(main):009:2>     return_true
> irb(main):010:2>   end
> irb(main):011:1> end
> => nil
> irb(main):012:0> Mod2.test
> NameError: undefined local variable or method `return_true' for 
> Mod2:Module

Mod2 itself does not have that method; if you had defined return_true 
as 'self.return_true' then it would have worked. Or you could have 
called 'module_method :return_true', I think. Otherwise, those methods 
get added as instance methods. You can mix them into a class:

 >> module Mod1
 >>   def return_true
 >>     true
 >>   end
 >> end
=> nil
 >> module Mod2
 >>   include Mod1
 >>   def test
 >>     return_true
 >>   end
 >> end
=> nil
 >> Mod2.test
NoMethodError: private method `test' called for Mod2:Module
         from (irb):111
 >> class Klass
 >>   include Mod2
 >> end
=> Klass
 >> Klass.new.test
=> true

cheers,
--Mark