From: daz <dooby@...10.karoo.co.uk>
Date: 2005-09-28T06:36:43+09:00
Subject: Re: Object private methods


Paolino wrote:
> Hello
>
>   I noticed that Object private methods are available everywhere.
> This I noticed exploring 'main' instance defining a method
>
> Can I have some explanation on this form of globalizing ?
>


It's useful to have some methods available almost anywhere ...

   $_ = 'A B C'
   puts split   #  there are two of the private methods
   #-> A
   #-> B
   #-> C

.... but not *everywhere* ...

   puts 3.split

   #-> ... private method `split' called for 3:Fixnum (NoMethodError)

There is no 'split' method for Fixnum.
Fixnum inherits from Object and a 'split' was found but, fortunately,
a sensible error message was produced before disaster struck.


We can define a (silly) split for Fixnum:

   class Fixnum
     def split
       self / 2.0
     end
   end

   puts 3.split
   #-> 1.5

.... and we can make it private:

   class Fixnum
     private :split
   end

   puts 3.split
   #-> ... private method `split' called for 3:Fixnum (NoMethodError)

.... but from within Fixnum, it's not private:

   class Fixnum
     def splitter
       split # <-----XXXXX
     end
   end

   puts 5.splitter
   #-> 2.5

So when we use 'puts' or 'split', or any other of the Kernel methods,
without a dot in front of them ("no receiver"), our homeland is a
place provided for us where all of those methods are non-private.
(A bit like standing to the left of the arrow   <-----XXXXX
  ... right inside an object)          <ROCK>

How warm and fluffy do you feel now ?  ;)


daz

Chorus: <i>Quit clownin', goof</i>