From: Stefano Crocco <stefano.crocco@...>
Date: 2007-08-23T21:56:47+09:00
Subject: Re: What is the difference between :, ::, . ?

Alle gioved� 23 agosto 2007, Gabriel Dragffy ha scritto:
> Hi, I'm still confused when to use :: or : or . to access namespaces
> and methods. Could someone please tell me concisely when each should
> be used?
>
> Many thanks
>
> Gabriel

* The dot (.) is used to access a method of an object (remember that 
class/module methods are simply instance methods of the class object). For 
example:

  "a string".capitalize
  1.ceil
  [1, 2, 3].uniq
  Regexp.escape

* The double colon (::) operator is used to access a constant contained in a 
module or class (remember that classes and modules are usually stored in 
constants). It can also be used to access class/module methods (but I think 
this is not much used)

  Regexp::EXTENDED        #a constant in the Regexp class
  Enumerable::Enumerator  #a class in the Enumerable modules
  File::exist?            #a class method of the File class

* The colon (:) operator has nothing to do with namespaces. Its only use, as 
far as I remember, is in the ternary operator ?
 
  a ? b : c

which is equivalent to

  if a then b
  else c
  end

Besides, a colon is also used in Symbol literals:

:a_symbol

which is the same as 'a_symbol'.to_sym.

I hope this helps

Stefano