Swift 2 to Swift 3.0 motionManager

Question

I am converting an app from swift 2 to swift 3 and I'm trying to use the CMMotionManager, but it gives me this error when I try to call the .startAccelerometerUpdates() function... No clue what's wrong though.

This is how I initialize the manager:

let motionManager = CMMotionManager()

Trying to call the function:

    motionManager.startAccelerometerUpdates(to: OperationQueue.main) { [weak self] (data: CMAccelerometerData?, error: NSError?) in
        self!.outputAccelerationData(data!.acceleration)
    }

Error: Cannot convert value of type '(CMAccelerometerData?, NSError?) -> ()' to expected argument type 'CMAccelerometerHandler' (aka '(Optional, Optional) -> ()')

Thanks!

Answer 1

The cryptic error message boils down to this: in Swift 3 NSError is bridged to Error instead. Write your code like this and the problem should go away:

motionManager.startAccelerometerUpdates(to: OperationQueue.main) { [weak self] (data: CMAccelerometerData?, error: Error?) in

Answer 2

There are many changes in Swift3. Especially in expressions. Many NS suffix of types are removed such as NSError to Error, NSData to Data. Therefore, change NSError to Error. And if you want to prevent performance issue by multiple instances of CMMotionManager, use SwiftyMotionManager.