From: Gary Wright <gwtmp01@...>
Date: 2009-12-15T13:54:36+09:00
Subject: Re: does module have instance_methods?


On Dec 14, 2009, at 11:25 PM, Ruby Newbee wrote:

> I'm still confused, since module can't be instantiated, why it has the
> instance methods?
> 
> irb(main):162:0> module Mymod
> irb(main):163:1>   def myway;end
> irb(main):164:1> end
> => nil
> irb(main):165:0> Mymod.respond_to? :myway
> => false
> irb(main):166:0> Mymod.instance_methods
> => [:myway]

You can think of a module as a container for method definitions.  By storing the definitions in a module you can reuse the methods without having to duplicate code by 'including' the module in a class or even another module:

module A
  def a1; "method a1"; end
  def a2; "method a2"; end
end

class B
  include A
end

B.new.a1
B.new.a2

class C
  include A
end

C.new.a1
C.new.a2

# You can even next modules within modules:

module D
  include A
end

class E
 include D
end

E.new.a1