From: dblack@...
Date: 2007-01-26T09:21:30+09:00
Subject: Re: Ruby language question

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Hi --

On Fri, 26 Jan 2007, Stefano Crocco wrote:

> Alle 01:02, venerd=C3=AC 26 gennaio 2007, Neville Franks ha scritto:
>> Hi, I've been working on adding Ruby language support to our IDE "ED for
>> Windows" the past few weeks and am stuck understanding the marked
>> statement in this code:
>>
>>    module Mod
>>      def size
>>        @size
>>      end
>>      def size=3D(val)   # what does this mean
>>        @size =3D val
>>      end
>>    end
>>
>> None of the reference material I've found so far shows this. I saw it in
>> the documentation for: attr(symbol, writable=3Dfalse) =3D> nil
>>
>> Thanks,
>> Neville
>
> def size=3D(val) is simply the definition of a method called size=3D, whi=
ch
> accepts the parameter val. It's the ruby way of allowing write access to =
an
> instance variable.

I'd put a slightly different spin on it.  Ruby lets you put a final =3D
on method names, and gives you the nice calling syntax:

   obj.x =3D 1    # prettified version of obj.x=3D(1)

The existence of the =3D-methods doesn't pertain directly to instance
variables.  You could write:

   def call_me_ishmael
     @name =3D "Ishmael"
   end

and you could also write:

   def name=3D(name)
     puts "You can't name me!"
   end

and so on.

Lots of =3D-methods (including all of those created with attr_writer)
involve writing to instance variables; but that's a conventioned
layered on top of the way it works, rather than being the way it works
itself.


David

--=20
Q. What is THE Ruby book for Rails developers?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
    (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)
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