From: konsu <konsu@...>
Date: 2006-02-16T10:38:27+09:00
Subject: Re: why does this freeze not work?

thank you. i understand.

then attr_accessor seems to be the only way. but one can always re-open my 
object and change the @id attribute... that is why i wanted to freeze the 
reference variable and not the object itself.

konstantin

"rcoder" <rcoder@gmail.com> wrote in message 
news:1140052087.338798.124690@o13g2000cwo.googlegroups.com...
> Freezing affects the object on which you call the 'freeze' method, not
> the context in which it's assigned to a name. In your example, you're
> simply freezing a Fixnum instance representing the number 1. Then, when
> you assign a new value to the 'id' instance attribute, you're changing
> which object it points to, rather than overwriting the original object.
>
> This is because variables in Ruby are references to objects, not chunks
> of memory. Object mutation happens via method call, not assignment.
>
> If you were to freeze your instance of C, you would get behavior more
> like you expect:
>
> c = C.new(1)
> c.freeze
> c.id = 2 # raises TypeError
>
> If you only want to prevent the 'id' attribute from being overwritten,
> just declare it with 'attr_reader', instead of 'attr_accessor'.
>
> -Lennon
>