before.rb

    def before(method_sym, &block)
      old_method = self.instance_method(method_sym)
      if old_method.arity == 0
        define_method(method_sym) do
          block.call
          old_method.bind(self).call
        end
      else
        define_method(method_sym) do |*params|
          old_method.bind(self).call(*block.call(*params))
        end
      end
    end