From: Joel VanderWerf <vjoel@...>
Date: 2003-06-02T00:21:02+09:00
Subject: Re: Advantages of Symbols over constants

Marek Janukowicz wrote:
> I wonder what are the advantages of using symbols over constants.  For
> example: I want to define representation of SQL comparison operators. If
> I use constants - I have to define them, but I don't have to do explicit
> check when using them (because exception will be raised on non-existing
> constant). It is also easy to see which operators are defined when
> looking at the source code. Another advantage - constants have
> namespaces: they can be defined in the class scope. If I use symbols - I
> don't have to define them, but I need to verify whether the symbol is
> valid. I have also to write additional documentation to indicate valid
> Symbols for operators. 
> 
> I find kind of general tendency on this group to recommend using symbols
> rather then constants. From what I wrote above I'd rather use constants.
> Could you please explain me why should I use symbols? Am I missing some
> important symbols advantage?

One advantage of symbols is that they know how to print themselves, but 
you can of course get this advantage with constants that refer to symbols:

   UP = :up
   DOWN = :down

   x = UP
   puts "You are going #{x}"

Another advantage with constants is that, if you want to change the 
value, there's only one spot in the code to change and you don't break 
the API.