原文地址：
http://www.yifeiyang.net/the-environment-of-developing-skills-iphone-paper-11/
其中我的设备SDK路径是：
IOS 设备用
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs
iPhone 模拟器用
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs