gistfile1.rb

class MyClass

  def abc(i)
    p "abc"
    p i
    42
  end

end

module StreetWalker

  def self.included(base)
    base.extend(self)
  end

  def hook_before(method, clazz, &block)
    temp_method = method.to_s+"_before_hook"
    hook(method, temp_method, clazz, block, nil)
  end

  def hook_after(method, clazz, &block)
    temp_method = method.to_s+"_after_hook"
    hook(method, temp_method, clazz, nil, block)
  end


  private

  def hook(method, temp_method, clazz, before_block, after_block)
    clazz.instance_eval do
      alias_method temp_method, method

      define_method(method) do |*args|
        before_block.call if before_block
        result = send(temp_method, *args)
        after_block.call(result) if after_block
      end
    end
  end
end

module MyClassTestHooks

  include StreetWalker

  hook_before :abc, MyClass do |result|
    p "BEFORE!"
  end

  hook_after :abc, MyClass do |result|
    p "AFTER"
    p "Result > "+result.to_s
  end

end

v = MyClass.new
v.abc 1