From: Stefano Crocco <stefano.crocco@...>
Date: 2010-10-15T00:22:49+09:00
Subject: Re: Freeze method doesn't work

On Thursday 14 October 2010, Sergey U. wrote:
> |Freeze should prevent further modifications to 'var'...

No. freeze prevents modifications to the object contained in var. For example:

str = "hello"
str.upcase!
puts str
=> HELLO
str.freeze
str.downcase!
=> RuntimeError: can't modify frozen string

str1 = str
str1.downcase!
=> RuntimeError: can't modify frozen string

Note that freeze is useless on classes (like Integer or Symbol) which don't 
have destructive methods.

The nearest you can come to prevent modifications to a variable is to use a 
constant instead (but remember that ruby allows you to assign a different 
value to a constant, it just emits a warning). However, the object the 
constant contains can be freely modified:

CONST="hello"
CONST.upcase!
puts CONST
"HELLO"
CONST="bye"
=> warning: already initialized constant CONST
puts CONST
=> "bye"

If you also want to prevent modifications to the object in the constant, 
freeze it.

I hope this helps

Stefano