ios - Swift optional type issue -

so i'm new @ swift , ios programming. i'm trying record accelerometer , gyroscope date , display on screen. tutorials managed finish code , kind of understand code. keep getting errors. , if follow suggestion xcode gives me more errors..

so code:

import uikit import coremotion  class viewcontroller: uiviewcontroller {      //instance variables      var currentmaxaccelx: double = 0.0     var currentmaxaccely: double = 0.0     var currentmaxaccelz: double = 0.0      var currentmaxrotx: double = 0.0     var currentmaxroty: double = 0.0     var currentmaxrotz: double = 0.0      var motionmanager = cmmotionmanager()       //outlets      @iboutlet var accx: uilabel?     @iboutlet var accy: uilabel?     @iboutlet var accz: uilabel?     @iboutlet var maxaccx: uilabel?     @iboutlet var maxaccy: uilabel?     @iboutlet var maxaccz: uilabel?     @iboutlet var rotx: uilabel?     @iboutlet var roty: uilabel?     @iboutlet var rotz: uilabel?     @iboutlet var maxrotx: uilabel?     @iboutlet var maxroty: uilabel?     @iboutlet var maxrotz: uilabel?      //functions      @ibaction func resetmaxvalues() {         currentmaxaccelx = 0         currentmaxaccely = 0         currentmaxaccelz = 0          currentmaxrotx = 0         currentmaxroty = 0         currentmaxrotz = 0     }      override func viewdidload() {          self.resetmaxvalues()          motionmanager.accelerometerupdateinterval = 0.2         motionmanager.gyroupdateinterval = 0.2          //start recording data          motionmanager.startaccelerometerupdatestoqueue(nsoperationqueue.currentqueue(), withhandler: {(accelerometerdata: cmaccelerometerdata!, error: nserror!) -> void in             self.outputaccelerometerdata(accelerometerdata.acceleration)             if (error != nil) {                 print("\(error)")             }         })          motionmanager.startgyroupdatestoqueue((nsoperationqueue.currentqueue()), withhandler: {(gyrodata: cmgyrodata!, error: nserror!) -> void in             self.outputrotationdata(gyrodata.rotationrate)             if (error! = nil) {                 print("\(error)")             }         })          super.viewdidload()      }      func outputaccelerometerdata(acceleration: cmacceleration) {          accx?.text = "\(acceleration.x).2fg"          if fabs(acceleration.x) > fabs(currentmaxaccelx) {             currentmaxaccelx = acceleration.x         }          accy?.text = "\(acceleration.y).2fg"          if fabs(acceleration.y) > fabs(currentmaxaccely) {             currentmaxaccely = acceleration.y         }          accz?.text = "\(acceleration.z).2fg"          if fabs(acceleration.z) > fabs(currentmaxaccelz) {             currentmaxaccelz = acceleration.z         }          maxaccx?.text = "\(currentmaxaccelx) .2f"         maxaccy?.text = "\(currentmaxaccely) .2f"         maxaccz?.text = "\(currentmaxaccelz) .2f"      }      func outputrotationdata(rotation: cmrotationrate) {          rotx?.text = "\(rotation.x).2fr/s"          if fabs(rotation.x) > fabs(currentmaxrotx) {             currentmaxrotx = rotation.x         }          roty?.text = "\(rotation.y).2fr/s"          if fabs(rotation.y) > fabs(currentmaxroty) {             currentmaxroty = rotation.y         }          rotz?.text = "\(rotation.z).2fr/s"          if fabs(rotation.z) > fabs(currentmaxrotz) {             currentmaxrotz = rotation.z         }        }        override func didreceivememorywarning() {         super.didreceivememorywarning()         // dispose of resources can recreated.     }    } 

and error keep getting want start recording data; value of optional type 'nsoperationqueue?' not unwrapped; did mean use "!" or "?"?

sorry if stupid question want understand stuff!

thanks in advance!!

since nsoperationqueue optional, need force unwrap using !.

so, replace nsoperationqueue.currentqueue() nsoperationqueue.currentqueue()!.

you can go through apple documentation , blog understanding swift optionals.