说明：  初学Brew时，最烦人的就是接口的定义了，一大堆的宏，让人不知所云。这里，将以helloworld为例，我们一步一步揭开它的神秘面纱
(Begin study Brew, the most annoying is the definition of the interface, and a bunch of macros, people incomprehensible. Here will helloworld example, our step-by-step to uncover the mysterious veil)