From: Robert Klemme <bob.news@...>
Date: 2004-03-31T21:59:22+09:00
Subject: Re: How are Symbol objects used


"gabriele renzi" <surrender_it@remove.yahoo.it> schrieb im Newsbeitrag
news:tncl60hesfj7dcfgl5b3ja6uio2ak95if2@4ax.com...
> il Wed, 31 Mar 2004 23:23:46 +1200, "Robo" <robo@mars.com> ha
> scritto::
>
> > Symbols are like Atoms in other languages -- they are invariant, and a
> >> symbol only creates a new object if it's the first time it's used.
> >
> >I've been wondering about symbols as well. What are some examples of a
good
> >place to use symbols?
>
> when you use something related to reflection
> (method(:sym) is an example)
>
> when you need a constant meaning something, insted of the C-like
> Module::CONST
> you can just use :const
> :const is just like a number (immutable and so on) but it has the
> plus have being meaningful.

Yep.

> in general, I even believe using symbols is safer than using string.
> If you are using a string and do not need it's features (take a look
> at String.instance_methods ) you may think of using a symbol (even if
> not everything is allowed as a symbol), avoiding possibly messing up
> something by changing the string.

No, in that case you use #freeze.  You should make it only dependent on
the semantics and not on the methods you actually use.  It's perfectly ok
to have a string constant, when it's appropriate - even if you don't need
to change it.  Apart from that methods might not accept a Symbol.  I'd
always write

File.open( "foo" ) {|io| ... }

instead of

File.open( :foo ) {|io| ... }

whiel yields an invalid argument anyway.

    robert