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

I know there's already plenty of answers but just to note what happened in my case:

I created the ViewController on the storyboard first and then I created the class, I don't know why this was an error because both class names where identical, but by rewriting the class name on the storyboard helped to "link" correctly the view controller and its file. First create file then ViewController on storyboard to prevent this error.