设备旋转通知无法按预期方式运行iOS Swift

Question

    func shouldirotate(){

    var whichwaywhere: String {

        if UIDevice.currentDevice().orientation == UIDeviceOrientation.LandscapeLeft {
            return "left"
        }
        if UIDevice.currentDevice().orientation == UIDeviceOrientation.LandscapeRight {
            return "right"
        }
        if UIDevice.currentDevice().orientation == UIDeviceOrientation.PortraitUpsideDown {
            return "down"
        }
        return "I don't Care"
    }
    println(whichwaywhere)
}

when I create a function that continuously checks itself, (attaching shouldirotate to a NSTimer) I can get the orientation checked. How could I tell the function to run when UIDeviceOrientationDidChangeNotification activates?

To get UIDeviceOrientationDidChangeNotification running I have a variable:

var rotatenote: Bool = UIDevice.currentDevice().generatesDeviceOrientationNotifications

and in the ViewDidLoad override I have:

override func viewDidLoad() {
    UIDevice.currentDevice().beginGeneratingDeviceOrientationNotifications()
    rotatenote = true
}

Is this the correct way to use and declare this property? how can I get the function to run off of DeviceOrientationNotification?

PS: I have rotatenote = true in the ViewDidLoad because if I try to attach it to the variable declaration like usual, it says "cannot assign to the result of this expression." See Below

var rotatenote: Bool = UIDevice.currentDevice().generatesDeviceOrientationNotifications = true

Answer 1

There are several ways to do this. Not sure what OS you are worried about, but in iOS 8 you've got two easy options. You can either register an observer for

UIDeviceOrientationDidChangeNotification

or you can override

func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator)

You should not need

UIDevice.currentDevice().beginGeneratingDeviceOrientationNotifications()

So either in viewDidLoad add:

NSNotificationCenter.defaultCenter().addObserver(self, selector: "functionThatYouWantTriggeredOnRotation", name:
        UIDeviceOrientationDidChangeNotification, object: nil)

Where you have a function functionThatYouWantTriggeredOnRotation that does the calculation...

Alternatively you can just provide the override for viewWillTransition and not have to add an observer for the UIDeviceOrientationDidChangeNotification

override func viewWillTransitionToSize(size: CGSize,
      withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator)
{
    if UIDevice.currentDevice().orientation.isLandscape {
            //do your thing
        }
}