If someone wants the answer, I think I just got it. Try this:
override func supportedInterfaceOrientations() -> UIInterfaceOrientationMask {
return UIInterfaceOrientationMask.Portrait.toRaw().hashValue | UIInterfaceOrientationMask.PortraitUpsideDown.toRaw().hashValue
}
Hope it helps !
EDIT :
To force rotation, use the following code :
let value = UIInterfaceOrientation.LandscapeRight.rawValue
UIDevice.currentDevice().setValue(value, forKey: "orientation")
It works for iOS 7 & 8 !