I had this problem today when I decided to open Xcode and start working. It just crushed every time I tried to open it. What to do in this situation? Easy. Just delete xcuserdata from the project. To do this:
- go to your project folder in Finder
- right click .xcodeproj file (or .xcworkspace file if you use Cocoapods) and choose Show Package Contents
- delete xcuserdata folder
