From: Jacob Fugal <lukfugl@...>
Date: 2005-04-16T04:59:14+09:00
Subject: Re: Why specify module names redundantly in Modules?

On 4/15/05, Chris <newsbot@cox.net> wrote:
> <RubyNubyAlert>
> Doing my best to convert from Perl to Ruby, and mainly loving every
> minute of it.
> 
> But I have a question about Modules...  Why when I declare a Module, do
> I have to prefix all the routines in that module with the module name
> (or routines outside the module don't see it)?  I don't get that?
> Isn't this kind of redundant?  For instance, I can't do this:
> 
> Module Foo
>    def bar
>       "bar"
>    end
> end
> 
> puts Foo.bar
> 
> I have to do this:
> 
> Module Foo
>    def Foo.bar
>       "bar"
>    end
> end

I know there's a reason for this, but I'll leave it to the experts to
explain that. Meanwhile, let me show some alternate uses:

#------------------------------------

  module Foo
    def bar
      puts "bar"
    end
  end

  # Add bar as a singleton method of class A's metaobject.

  class A
    extend Foo
  end

  A.bar # => prints "bar"

  begin
    A.new.bar # => raises "undefined method `bar'"
  rescue Exception => e
    puts e
  end

  # Add bar as a public instance method of B.

  class B
    include Foo
  end

  B.new.bar # => prints "bar"

  begin
    B.bar # => raises "undefined method `bar'"
  rescue Exception => e
    puts e
  end

  # Add bar as a singleton method of c. Won't exist for other objects
of the same class.

  class C
  end

  C.new.extend( Foo ).bar # => prints "bar"

  begin
    C.bar # => raises "undefined method `bar'"
  rescue Exception => e
    puts e
  end

  begin
    C.new.bar # => raises "undefined method `bar'"
  rescue Exception => e
    puts e
  end

#------------------------------------

Hope that helps make things a little clearer.

Jacob Fugal