轉載 https://www.jianshu.com/p/37ee30ed76ee
下載最新版Xcode #include <string>報錯 'string' file not found C++頭文件缺失問題
將對應文件拷貝到最新版XCode對應目錄下
真機：
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/c++
模擬器：
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/c++
Xcode9 C++頭文件github鏈接：https://github.com/DeCori/Xcode9-cpp.git