xcode 'boost/config/user.hpp' file not found

Just remove the cache and the third_party folder in react-native in node modules

 rm -r ~/.rncache rm -r <your-project>/node_modules/react-native/third_party

ios xcode boost react-native npm

For those who are using react-native version > 0.57

rm -r ~/Library/Caches/com.facebook.ReactNativeBuildrm -r <your-project>/node_modules/react-native/third_party

ios xcode boost react-native npm

I just run the command : npm install and fixed the issue..

CodeHunter