转载 https://www.jianshu.com/p/37ee30ed76ee
下载最新版Xcode #include <string>报错 'string' file not found C++头文件缺失问题
将对应文件拷贝到最新版XCode对应目录下
真机：
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/c++
模拟器：
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/c++
Xcode9 C++头文件github链接：https://github.com/DeCori/Xcode9-cpp.git