No error printed however function doesn't run

Question

I am attempting to make a camera view appear, as you can see in my code below I have it set up to display any errors and not break the program if any errors occur, however when I do run this code no error occurs or camera view is displayed. I am running it on an actual phone and the phone did request if it had permission to use the camera. Below is the code

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)

    captureSession = AVCaptureSession()
    captureSession?.sessionPreset = AVCaptureSessionPreset1920x1080

    let backCamera = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
    var input : AVCaptureDeviceInput?
    let error : NSError?
    do {
        input = try AVCaptureDeviceInput(device: backCamera)
    } catch let error as NSError? {
        print(error)



        if error == nil && (captureSession?.canAddInput(input))!{
            captureSession?.addInput(input)

            videoOutput = AVCaptureVideoDataOutput()
            //videoOutput?.outputSettings = [AVVideoCodecKey : AVVideoCodecKey]

                if ((captureSession?.canAddOutput(videoOutput)) != nil){
                    captureSession?.addOutput(videoOutput)

                    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
                    previewLayer?.videoGravity = AVLayerVideoGravityResizeAspect
                    previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.Portrait
                    cameraView.layer.addSublayer(previewLayer!)
                    captureSession?.startRunning()
            }
        }
    }

}

Answer 1

Don't put code in the catch. That is if something goes wrong.

do {
    input = try AVCaptureDeviceInput(device: backCamera)
} catch let error as NSError? {
    print(error)
    return//Stop rest of code
}
if (captureSession?.canAddInput(input))!{
        captureSession?.addInput(input)

        videoOutput = AVCaptureVideoDataOutput()
        //videoOutput?.outputSettings = [AVVideoCodecKey : AVVideoCodecKey]

            if ((captureSession?.canAddOutput(videoOutput)) != nil){
                captureSession?.addOutput(videoOutput)

                previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
                previewLayer?.videoGravity = AVLayerVideoGravityResizeAspect
                previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.Portrait
                cameraView.layer.addSublayer(previewLayer!)
                captureSession?.startRunning()
        }
    }