Simply build and run the iOSFortunes.xcodeproj in the iOSFortunes directory. It should Just Work™️.
In your terminal, cd to ReactFortunes and run either npm install or yarn install.
Then run react-native run-ios to start the app on the iOS simulator.
If you get the error config.h not found, run the following command from the ReactFortunes directory:
cd node_modules/react-native/third-party/glog-* && ../../scripts/ios-configure-glog.sh;
If you get an error like configure: error: C compiler cannot create executables, make sure you have the path to Xcode selected correctly using xcode-select and that the path to your Xcode does not have any spaces in it! Crazy stuff, huh?
After that completes, run react-native run-ios again.
Presentation where I discuss and compare iOS and React Native implementations.