From: Robert Klemme <shortcutter@...>
Date: 2009-03-26T01:50:10+09:00
Subject: Re: appending an array to a frozen array

2009/3/25 James French <James.French@naturalmotion.com>:
> Ah, I understand - thanks. My next question is - is it possible to prevent this?

Since you are using an instance variable you control how it is
accessed. So, yes.  If you want to know whether there is a hard way to
prevent reassignment to instance variables, the only safe way I know
off the top of my head is to freeze the owner:

irb(main):001:0> o=Object.new
=> #<Object:0x10171ed8>
irb(main):002:0> o.instance_variable_set "@foo", 1
=> 1
irb(main):003:0> o
=> #<Object:0x10171ed8 @foo=1>
irb(main):004:0> o.freeze
=> #<Object:0x10171ed8 @foo=1>
irb(main):005:0> o.instance_variable_set "@foo", 2
RuntimeError: can't modify frozen object
        from (irb):5:in `instance_variable_set'
        from (irb):5
        from /opt/bin/irb19:12:in `<main>'
irb(main):006:0>

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end