ios - 调用 viewdidload 图像中的 Swift 2 额外参数错误

Question

我正在使用 Xcode 7 将我的应用程序更新到 Swift 2。这是我的 ViewController viewDidLoad 代码。

 override func viewDidLoad() {
        super.viewDidLoad()

    // Get an instance of the AVCaptureDevice class to initialize a device object and provide the video
    // as the media type parameter.
    let captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)

    // Get an instance of the AVCaptureDeviceInput class using the previous device object.
    var error:NSError?

    let input: AnyObject! = AVCaptureDeviceInput.deviceInputWithDevice(captureDevice, error: &error)

    if (error != nil) {
        // If any error occurs, simply log the description of it and don't continue any more.
        print("\(error?.localizedDescription)")
        return
    }

    // Initialize the captureSession object.
    captureSession = AVCaptureSession()
    // Set the input device on the capture session.
    captureSession?.addInput(input as! AVCaptureInput)

    // Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
    let captureMetadataOutput = AVCaptureMetadataOutput()
    captureSession?.addOutput(captureMetadataOutput)

    // Set delegate and use the default dispatch queue to execute the call back
    captureMetadataOutput.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
    captureMetadataOutput.metadataObjectTypes = supportedBarCodes

    // Initialize the video preview layer and add it as a sublayer to the viewPreview view's layer.
    videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
    videoPreviewLayer?.frame = view.layer.bounds
    view.layer.addSublayer(videoPreviewLayer!)

    // Start video capture.
    captureSession?.startRunning()

    // Move the message label to the top view
    view.bringSubviewToFront(messageLabel)

    // Initialize QR Code Frame to highlight the QR code
    qrCodeFrameView = UIView()
    qrCodeFrameView?.layer.borderColor = UIColor.greenColor().CGColor
    qrCodeFrameView?.layer.borderWidth = 2
    view.addSubview(qrCodeFrameView!)
    view.bringSubviewToFront(qrCodeFrameView!)
}

在线

let input: AnyObject! = AVCaptureDeviceInput.deviceInputWithDevice(captureDevice, error: &error)

我收到错误 Extra argument error in call。我已经尝试使用方法 do{} 和 catch{} 但它不起作用，我总是会收到该错误。

我该如何解决？谢谢

Answer 1

Swift 2 引入了新的错误处理。要解决您遇到的问题，您需要 catch 错误而不是将 NSError 对象传递给 AVCaptureDevice 方法:

override func viewDidLoad() {
    super.viewDidLoad()

    do {
        let captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
        let input = try AVCaptureDeviceInput(device: captureDevice)
        // Do the rest of your work...
    } catch let error as NSError {
        // Handle any errors
        print(error)
    }
}

有关更深入的解释，请查看这篇文章:

Error Handling in Swift 2.0