From: Logan Capaldo <logancapaldo@...>
Date: 2006-03-11T02:01:03+09:00
Subject: Re: unextend ?


On Mar 10, 2006, at 8:42 AM, Ross Bamford wrote:

> On Fri, 2006-03-10 at 01:03 +0900, Dirk van Deun wrote:
>> A very short and simple question: is there a function to  
>> "unextend" an
>> object ?
>
> Might this suffice?
>
> class Object
>   def unextend(mod)
>     (mod.instance_methods +
>      mod.private_instance_methods +
>      mod.protected_instance_methods).uniq.each do |m|
>        instance_eval "undef #{m}"
>      end
>   end
> end
>
> class A
>   def each; yield 1; end
> end
>
> a = A.new
>
> a.extend(Enumerable)
> puts a.map { |e| e + 1 }
> # => 2
>
> a.unextend(Enumerable)
> puts a.map { |e| e + 1 }
> # => -:17: undefined method `map' for #<A:0xb7f837a0> (NoMethodError)
>
> -- 
> Ross Bamford - rosco@roscopeco.REMOVE.co.uk
>
>

I get  the feeling that could be dangerous. Since you do it in the  
context of Object, you may very well delete  methods implemented by  
the object that have the same names as ones in the module. One  
example I can think of is to_a. There is an Enumerable#to_a which  
which gives an array after iterating thru an object. Likewise there's  
an Array#to_a. That method, in object instance_eval'ed the way you  
have would delete Array's to_a all together. Of course #extend'ing   
an object apparently overwrittes the old methods anyway (as opposed  
to including it in the class, which inserts  the module into the  
inheritance chain). At least with my hack when you don't loose  
method's you've specifically implemented yourself.