From: Brian Mitchell <binary42@...>
Date: 2006-04-20T04:49:15+09:00
Subject: Re: overriding a class method

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.