From: dblack@...
Date: 2006-07-14T09:35:58+09:00
Subject: Re: Initialize a variable in an extended class

Hi --

On Fri, 14 Jul 2006, Eric Armstrong wrote:

>    Note: For a long time it wasn't clear to me that
>    it is impossible to initialize an instance variable
>    outside of a method. Coming from the Java world, I
>    just assumed that this would be legal:
>      class Foo
>        @bar = 2
>      end
>
>    But it isn't. (A fact that needs to be spelled out
>    somewhere, for Java types.)

I'm not sure what you mean by "somewhere".  It gets talked about and
explained regularly here, as well as in various books, wikis, etc.
The workings of instance variables are not a closely guarded secret
:-)

When you see this:

   @var

you are seeing an instance variable belonging to whatever object is,
at that point, playing the role of "self" (the default object).

At the top level of a class definition block, "self" is the class
object (Foo in your example).

So in your example, you've got an instance variable belonging to the
class object Foo.  There's no connection at all between this instance
variable and any instance variable that may come into being later when
some other object is "self" (including an instance of Foo).


David

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