From: Gregory Brown <gregory.t.brown@...>
Date: 2010-01-13T13:24:53+09:00
Subject: Re: Using underscores for "private" instance variables?

On Tue, Jan 12, 2010 at 9:11 PM, Jeff <cohen.jeff@gmail.com> wrote:
> On Jan 12, 9:48 am, Gregory Brown <gregory.t.br...@gmail.com> wrote:

> Gregory, that's interesting.  Maybe any Ruby library that reaches
> sufficent mass use will run into this problem.
>
> But I think the underscore doesn't really solve the problem, right?
>
> Let's say you use @_file in your module that I include.  You probably
> use #nodoc# around it so I don't even see it in the rdocs.  So then my
> class I'm about to do @file, but I think, someone might derive from my
> class, so I'd better call it @_file.  Collision again.

In either case, it's your fault if you don't read upstream source.
But if you're trying to make life easier downstream, it's less likely
to clash with @_file than it is with @file by accident.

But I agree, @_whatever is ugly and I'm not sure I will introduce it
into Prawn.   I just understand why the Rails guys did it after having
a bit of direct experience.

> So I say, let's not use the hard-to-read underscores, and document
> ivars in the rdocs like everything else.

I don't think that internal state benefits from public documentation,
as that just invites one more thing that can get out of date fast, and
invites more danger than it's worth.

I think one real solution is to avoid ivar references in modules
(using method calls), and prefer composition over sub-classing.  But
this is edging on the sort of discipline you'd find in functional
languages, which tends to feel a bit too stuffy for some folks.

I'm about to do some major refactoring in Prawn in the near future.  I
might play with these thoughts and see where they lead.   If I shake
anything loose that's worth sharing, I'll write it up on the RBP blog.

-greg