[swift-users] Lifetime of objects in `class` methods

[Nate Birkholz]

If I use these two classes:

class MotionManager {



    class func doTheThing(completionHandler: @escaping (CMDeviceMotion?)->()
) {

        print("in")

        let manager = CMMotionManager()

        manager.deviceMotionUpdateInterval = 0.01



        manager.startDeviceMotionUpdates(to: .main) { (motion, error) in

            print("out")

            completionHandler(motion)

        }

    }

}


class OtherManager {

    let manager: CMMotionManager



    init() {

        manager = CMMotionManager()

        manager.deviceMotionUpdateInterval = 0.01

    }



    func doTheThing(completionHandler: @escaping (CMDeviceMotion?)->() ) {

        print("in 2")

        manager.startDeviceMotionUpdates(to: .main) { (motion , error) in

            completionHandler(motion)

            print("out 2")

            self.manager.stopDeviceMotionUpdates()

        }

    }

}


let other = OtherManager()


other.doTheThing { (motion) in

    print(motion)

}


MotionManager.doTheThing { (motion) in

    print(motion)

}

The class method on MotionManager prints "in" but never prints "out". The
instance method version on. OtherManager works just fine, printing "in 2"
and "out 2". Clearly the CMMotionManager doesn't survive long enough to
finish its call, but I would have thought it would.

Is this a bug? Or am I just misunderstanding how the class method should
work?

-- 
Nate Birkholz
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