Error: Cannot read property 'UIAppFonts' of null

I had same issue not quite long, running react-native links will give you error. If you are using yarn simply run:

1. yarn remove react-native
2. yarn add react-native
3. Then run react-native link

This fixed it for me.

I had this problem and in my case it was because I had renamed the project but forgotten to update newname in a few folders and files.

I had this exact same problem. I had accidentally deleted by Info.plist file in my ios directory. Restoring it, fixed my issue.