Swift: Thread 1 signal SIGABRT

Question

After upgrading Xcode from 5 to 6 beta, almost every project gives me an unexpected error after running the application. There are some other posts with this title but the error

Answer 1

My issues with this started after I installed the legacy simulators (iOS7.1) under 'More Simulators' under the simulator build target. Xcode 6 and its native simulator had been running fine until then. What fixed it for me was to close Xcode, delete Derived Data, and under iOS Simulator in the simulator application choose "Reset Content and Settings" then restart the system.