From: Aleksei Guzev <aleksei.guzev@...>
Date: 2002-11-23T17:59:48+09:00
Subject: Re: Modifying objects in place


"Tim Bates" <tim@bates.id.au> wrote in message
news:200211231746.11909.tim@bates.id.au...
> How can I write a Foo.succ! method in my own class? When I try
> def succ!() self = self.succ end
> I get "Can't change the value of self"
>
> Tim Bates
> --
> tim@bates.id.au
>

self is a reference to the object(if the object is not of value-type). One
cannot change the reference.
You wish to change the the referenced value but not the reference itself.

class Foo
    def initialize(v)
        @a = v
    end
    def succ()
        return @a.succ
    end
    def succ!()
        @a = @a.succ
    end
end


irb(main):042:0> var = Foo.new(4)
#<Foo:0x28d3d50 @a=4>
irb(main):043:0> var.succ
5
irb(main):042:0> var.succ!
5
irb(main):042:0> var
#<Foo:0x28d3d50 @a=5>