From: Hal Fulton <hal9000@...>
Date: 2005-06-14T09:38:10+09:00
Subject: Re: are these the same?

Lowell Kirsh wrote:
> I'm wondering about the difference between writing something like
> 
> @x = ...
> and
> self.x = ...
> 
> from within a class. Are they the same thing? 

Not necessarily the same.

@x = ...       # assigns an instance variable
self.x = ...   # invokes a method called x= (which doesn't
                # exist in your example.

Now, having said they're different... if you add

   attr_accessor :x

then they are more the same.

Bear in mind that instance variables are accessed from the
"outside world" only via methods.

And when you say self.x within a class, you are basically
accessing it "from the outside" even though you are inside
the class (dumb analogy: You're in your house, and you
reach outside a window and then reach into the window next
to it "from outside").

Also bear in mind that if you (manually) define a method x=,
you *could* define it in a stupid or misleading way (just
as you *could* give misleading names to all your variables
and methods):

     def x=(val)
       puts "Ha, fooled you! I'm setting @y to 123!"
       @y = 123   # and not even using val
     end



Hope this helps...

Hal