所有代码都是放在同一个文件main.h中的-All code is placed in the same file main.h

苹果平台开发语言--Objective-c 包括一些基本的objc入门文档，和一些学习建议-Apple platform development language- Objective-c include some basic the objc entry document, and some learning recommendations

Object-c 语言介绍，基础的object-c 语言架构介绍-The Object-Cprogramming Language