I am trying to import various libraries which I can\'t remember their exact name. Unfortunately Xcode 6 (using swift) isn\'t auto completing th
This is the same as the correctly chosen answer above but just made slightly easier.
I've had to do it several times and in my testing you can skip restarting your mac.
1) Close Xcode
2) Terminal -> rm -rf ~/Library/Developer/Xcode/DerivedData/*
3) Terminal -> rm -rf ~/Library/Caches/com.apple.dt.Xcode
Restart Xcode and it should be back to normal.