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swift3core-motion

Using startDeviceMotionUpdates under Swift 3

Yes, I have seen a previous question on this, but I still can't get this to work. My previous Swift2 code was...

motionMgr.startDeviceMotionUpdatesToQueue(NSOperationQueue(), withHandler: handleMove)

which called:

func handleMove(motion: CMDeviceMotion?, error: NSError?) {
    ...
}

This has changed under Swift3, and now the startDeviceMotionUpdatesToQueue uses a closure. I can't for the life of me figure out how to call my existing method. I realize the NSError became Error and other minor changes, but the syntax of the call from the closure has me very confused.

Solution

  • This should work for you, there are just a few re-namings in Swift 3.

    motionMgr.startDeviceMotionUpdates(to: OperationQueue(), withHandler: handleMove)

func handleMove(motion: CMDeviceMotion?, error: Error?) {
    // ...
}

    The handler is of type CMDeviceMotionHandler which is defined as a typealias to a closure:

    typealias CMDeviceMotionHandler = (CMDeviceMotion?, Error?) -> Void

    We just need to provide a closure (or a function, since a function is a closure), that takes in two parameters (a CMDeviceMotion? and Error?) and returns nothing (Void).

    Alternatively, you could provide a closure instead of a function like so:

    motionMgr.startDeviceMotionUpdates(to: OperationQueue(), withHandler: { deviceMotion, error in
    // ...
})

    or use the new trailing closure syntax:

    motionMgr.startDeviceMotionUpdates(to: OperationQueue()) { deviceMotion, error in
    // ...
}