From: "David A. Black" <dblack@...>
Date: 2009-02-09T05:57:55+09:00
Subject: Re: best way to protect class instance variables

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On Mon, 9 Feb 2009, David Masover wrote:

> Mike Gold wrote:
>> Jes炭s Gabriel y Gal叩n wrote:
>> 
>>> This could save you from accidental changes, but somebody could always
>>> do this and trash your frozen array:
>>> 
>>> irb(main):017:0> class Blah
>>> irb(main):018:1> @blah = %w{nothing is really safe}
>>> irb(main):019:1> end
>>> 
>> 
>> Data from a closure cannot be overwritten in this way, and could qualify as 
>> being "really safe".
>> 
> But, you've already provided a method for breaking that anyway --
> define_method.
>
> So, someone could always do:
>
> blah = MyClass.blah.dup
> blah[0] = 5
> class << MyClass
> define_method :blah { blah }
> end

The blah in { blah } is going to be undefined there, because the class
definition block starts a new local scope. However, you can certainly
get that effect:

   def MyClass.blah
     # some wrong value
   end

and of course:

   MyClass.blah << 2

(unless it's frozen). I agree with your point about not programming on
the assumption that the other programmers who use your code are going
to sabotage your classes.


David

-- 
David A. Black / Ruby Power and Light, LLC
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