Xcode 6 Swift code completion not working

Question

Using Xcode 6 GM seed my code completion has stopped working. It was working the other day. I was trying to get the unwind segue work around to work. I had made an Objc head

Answer 1

There's an easier way to delete the Derived Data from within Xcode (no need to open finder or restart):

Xcode Organizer -> Projects -> (Your Project) -> Delete Derived Data