通过Terminal进入Xcode.app所在目录，可以找到相应的SDK路径，相关 的Framework的头文件也在改目录下。
示例如下：
Frameworks
/Applications/xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk/System/Library/Frameworks
头文件：
/Applications/xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk/System/Library/Frameworks/IOKit.framework/Headers