From: Kevin Olbrich <devlists-ruby-talk@...>
Date: 2006-04-20T06:02:04+09:00
Subject: Re: overriding a class method

Thanks!

I am slowly but surely getting the hang of this metaprogramming thing.

On Thursday, April 20, 2006, at 4:49 AM, Brian Mitchell wrote:
>On 4/19/06, Kevin Olbrich <devlists-ruby-talk@devlists.com> wrote:
>> Yeah, not looking to subclass.
>
>class A
>  def self.meth_a
>    puts "one"
>  end
>end
>
>class A
>  class << self; alias meth_a_old meth_a end
>  def self.meth_a
>    meth_a_old
>    puts "two"
>  end
>end
>
>Though I personally think use of alias for this sort of thing as a
>"hack" (just my opinion of course). Another technique is to use a
>lexical closure:
>
>class A
>  def self.meth_a
>    puts "one"
>  end
>end
>
>class A
>  old_a = method(:meth_a)
>  # The ugly part. This usually is nicer for instance methods.
>  # You could write this a few different ways but they are all
>  # ugly. Possibly something to factor out as a method.
>  sclass = class << self; self end
>  sclass.send :define_method, :meth_a do
>    old_a.call
>    puts "two"
>  end
>end
>
>Both are messy but one is less likely to collide or cause problems
>with other code (not to mention littering the class with aliases).
>
>Brian.
>


_Kevin

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