通过clang看OC底层C++文件

想了解oc底层的c++文件是怎样的，然后执行clang -rewrite-objc ViewController.m时报错

In file included from ViewController.m:9:
./ViewController.h:9:9: fatal error: 'UIKit/UIKit.h' file not found
#import <UIKit/UIKit.h>
        ^~~~~~~~~~~~~~~
1 error generated.

解决办法:

clang -x objective-c -rewrite-objc -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk xxxxx.m

可通过alias简化如下：

1、进入终端输入

vim ~/.bash_profile

2、在vim界面输入i进入编辑状态然后输入：

alias writeoctoc='clang -x objective-c -rewrite-objc -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk'

3、点esc退出编辑状态，再键入:wq（退出vim并保存），执行source ~/.bash_profile

4、进入你想要编译的文件目录

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5、执行writeoctoc xxx.m即可成功

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