So, one moment you’re app was running fine in the simulator and the next moment you get an error saying “The operation could not be completed. (LaunchServicesError error 0.)”
Bummer! When you check your logs (see ~/Library/Logs/CoreSimulator/CoreSimulator.log or ~/Library/Logs/CoreSimulator/[Device UDID]/system.log) you’ll find errors like “/<app name>.app did not have a CFBundleIdentifier in its Info.plist}”. And when you check your Info.plist all is fine there.
Don’t despair. You probably created a folder “Resources” in your Project Navigator. And while that’s a perfectly reasonable name for a project folder, XCode does not like that. All you have to do is rename the folder and chances are your project will run again.