无法在Swift中使用前置摄像头

我想构建前置摄像头，但即使我可以构建后置摄像头，也无法在 Swift 中构建前置摄像头。

当我只将“back”更改为“front”时，相机不起作用......

如何使用前置摄像头？

var captureSesssion: AVCaptureSession!
var stillImageOutput: AVCapturePhotoOutput?
var previewLayer: AVCaptureVideoPreviewLayer?
var captureDevice : AVCaptureDevice!

override func viewDidLoad() {
    super.viewDidLoad()

    captureSesssion = AVCaptureSession()
    stillImageOutput = AVCapturePhotoOutput()

    captureSesssion.sessionPreset = AVCaptureSessionPreset1920x1080 

    captureDevice = AVCaptureDevice.defaultDevice(withDeviceType: .builtInWideAngleCamera, mediaType: AVMediaTypeVideo, position: .front) 
    //When change "front" to "back", camera is built.

    do {
       let input = try AVCaptureDeviceInput(device: captureDevice)

       if (captureSesssion.canAddInput(input)) {
           captureSesssion.addInput(input)

           if (captureSesssion.canAddOutput(stillImageOutput)) {
               captureSesssion.addOutput(stillImageOutput)
               captureSesssion.startRunning() 

               previewLayer = AVCaptureVideoPreviewLayer(session: captureSesssion)
               previewLayer?.videoGravity = AVLayerVideoGravityResizeAspect 
               previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.portrait 

               self.view.layer.addSublayer(previewLayer!)

               previewLayer?.position = CGPoint(x: self.view.frame.width / 2, y: self.view.frame.height / 2)
               previewLayer?.bounds = self.view.frame
           }
       }
    }
    catch {
        print(error)
    }