From: Robert Klemme <shortcutter@...>
Date: 2011-10-05T00:58:46+09:00
Subject: Re: Operator Overloading

On Tue, Oct 4, 2011 at 5:52 PM, Dave Aronson
<rubytalk2dave@davearonson.com> wrote:
> On Tue, Oct 4, 2011 at 10:03, Brian Candler <b.candler@pobox.com> wrote:
>
>> (Of course, 'x' and 'self.x' are the same; you can write 'self.x' if you
>> think it's clearer)
>
> Not quite.  This is one of Ruby's little gotchas.  A naked "x" will be
> taken as a local variable in the method.  If you want to use an
> instance variable you *must* precede it with either "self." or "@".

The story is a bit more complex.

1. writing

"x = exp" will _always_ assign to a local variable.  If you want to
invoke the setter method you _must_ do "self.x = expr".

2. reading

"x" will access a local variable if it is defined and fall back to the
getter method if there is no variable.  "self.x" will always invoke
the getter method regardless whether there is a local variable or not.

Example:

$ ruby19 -e 'def x;1;end;public :x;def f;p x, self.x;x=99;p x, self.x;end;f'
1
1
99
1

Needless to say that it's not the best of practices to mix local
variables and properties of the same name. :-)

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/