From: Bertram Scharpf <lists@...>
Date: 2009-12-22T20:02:31+09:00
Subject: Re: Symbols vs. constants?

Hi,

Am Dienstag, 22. Dez 2009, 09:57:28 +0900 schrieb Sonja Elen Kisa:
> How are symbols and constant (capitalized) strings similar or
> dissimilar? They both seem to be used to store text that is not intended
> to change. In what situations should I use one or the other? How should
> I separate them in my brain?

Constants are variables:

  X = "hello"
  X = "bye"             # not allowed (just a warning)
  X.replace "bye"       # this is allowed!
  X.freeze
  X.replace "hi again"  # forbidden (TypeError)

But you can also freeze other variables:

  x = "foo"
  x.freeze
  x.replace "bar"       # forbidden (TypeError)

Symbols are objects but do not have no `replace' method neither
`sub', `gsub', `tr', `succ!', and what else could change its
contents.

  x = :foo
  X = :bar
  x.replace sth         # forbidden (NoMethodError)

Could it be that I didn't use `freeze' for years? Did I miss
something?

Bertram


-- 
Bertram Scharpf
Stuttgart, Deutschland/Germany
*
Discover String#notempty? at <http://raa.ruby-lang.org/project/step>.