gistfile1.txt

# Usage
require 'hookr'

class A
  include Hookr

  def b
    puts "bee"
  end
  
  before :b do
    puts "aye"
  end
  
  after :b do
    puts "cee"
  end
end

>> A.new.b
=> "aye"
=> "bee"
=> "cee"

hookr.rb

module Hookr
  module ClassMethods
    def before(target, &block)
      add_hook(:before, target, block)
    end
    
    def after(target, &block)
      add_hook(:after, target, block)
    end
    
    
    private
    def add_hook(hook, target, block)
      name = "_#{target}_#{hook}"
      
      alias_method name, target
      private target
      
      define_method(target) do |*args|
        block.call if hook == :before
        send(name)
        block.call if hook == :after
      end
    end
  end
  
  def self.included(base)
    base.extend(ClassMethods)
  end
end