Core Motion: Value of optional type 'NSOperationQueue?' not unwrapped

Question

I am following a tutorial from RayWenderLich's website, however, I am stuck on the part about Core Motion.

// CoreMotion
    // 1
    motionManager.accelerometerUpdateInterval = 0.2
    // 2
    motionManager.startAccelerometerUpdatesToQueue(NSOperationQueue.currentQueue(), withHandler: {
        (accelerometerData: CMAccelerometerData!, error: NSError!) in
        // 3
        let acceleration = accelerometerData.acceleration
        // 4
        self.xAcceleration = (CGFloat(acceleration.x) * 0.75) + (self.xAcceleration * 0.25)
    })

I try fixing the error, but I end up with more errors.

Any help is appreciated. Thank you.

Answer 1

The NSOperationQueue's currentQueue returns an optional so you need to unwrap the optional, NSOperationQueue.currentQueue()!.

// CoreMotion
// 1
motionManager.accelerometerUpdateInterval = 0.2
// 2
motionManager.startAccelerometerUpdatesToQueue(NSOperationQueue.currentQueue()!, withHandler: {
    (accelerometerData: CMAccelerometerData?, error: NSError?) in
    // 3
    let acceleration = accelerometerData.acceleration
    // 4
    self.xAcceleration = (CGFloat(acceleration.x) * 0.75) + (self.xAcceleration * 0.25)
})

Also, the closure that you use as handler has wrong parameter types. It's typealias CMAccelerometerHandler = (CMAccelerometerData?, NSError?) -> Void