swift - Metal iOS gives compile error -

import uikit import metal import quartzcore  class viewcontroller: uiviewcontroller {  var device: mtldevice! = nil var metallayer: cametallayer! = nil  override func viewdidload() {     super.viewdidload()     // additional setup after loading view, typically nib.     device = mtlcreatesystemdefaultdevice()     metallayer = cametallayer()          // 1     metallayer.device = device           // 2     metallayer.pixelformat = .bgra8unorm // 3     metallayer.framebufferonly = true    // 4     metallayer.frame = view.layer.frame  // 5     view.layer.addsublayer(metallayer)   // 6 }  override func didreceivememorywarning() {     super.didreceivememorywarning()     // dispose of resources can recreated. }   } 

when have in viewcontroller.swift, error "use of undeclared type cametallayer" though i've imported metal , quartzcore. how can code work?

metal code doesn't compile on simulator. try compiling device.