From: dblack@...
Date: 2006-07-13T20:24:03+09:00
Subject: Re: re-define class method

Hi --

On Thu, 13 Jul 2006, David Chelimsky wrote:

> On Jul 13, 2006, at 5:33 AM, dblack@wobblini.net wrote:
>
>> On Thu, 13 Jul 2006, David Chelimsky wrote:
>> 
>>> thing_singleton_class = class << Thing; self; end
>>> thing_singleton_class.send(:define_method, :class_method, proc { 
>>> "replaced" })
>>> 
>>> Thing.class_method
>>> => "replaced"
>> 
>> Don't forget that you can do this much more concisely (unless you have
>> a specific need to go the long way round):
>>
>>  def Thing.class_method
>>    "replaced"
>>  end
>
> Thanks David. I definitely appreciate the conciseness of this, and will use 
> that when I know the type. The problem I'm working on requires a solution to 
> replacing singleton methods on arbitrary types at runtime, so I think I have 
> to stick w/ the more cryptic version. Unless you have a different suggestion 
> - I'm just getting my head wrapped around metaprogramming and singleton 
> classes, so all suggestions are most welcome.

There's an intermediate version, which might be usable depending on
how much you know in advance:

   class << Thing
     def class_method
       "replaced"
     end
   end

When you need a less concise version, because you're determining
things more dynamically, I would personally tend to use class_eval and
define_method without send:

meth = "class_method"
l = lambda { "replaced" }
(class << Thing; self; end).class_eval { define_method(meth,&l) }

And hopefully we'll eventually have a Kernel#singleton_class method to
make it all a little neater :-)


David

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