错误：输入'String！'没有会员'视频'

Question

import UIKit
import AVKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

//start camera

        let captureSession = AVCaptureSession()

        guard let captureDevice =
           AVCaptureDevice.default(for: .video) else { return }
        guard let input = try? AVCaptureDeviceInput(device:
                captureDevice ) else { return }
        captureSession.addInput(input)

        captureSession.startRunning()
    }
}

我收到此行中的错误（对于： .video ）：

AVCaptureDevice.default(for: .video) else { return }

Answer 1

用AVMediaTypeVideo替换AVMediaType.video对我有用。

Answer 2

方法

class func `default`(_ deviceType: AVCaptureDevice.DeviceType, 
             for mediaType: AVMediaType?, 
        position: AVCaptureDevice.Position) -> AVCaptureDevice?

接受DeviceType，可以是：

AVCaptureDeviceTypeBuiltInMicrophone
AVCaptureDeviceTypeBuiltInWideAngleCamera
AVCaptureDeviceTypeBuiltInTelephotoCamera
AVCaptureDeviceTypeBuiltInDualCamera
AVCaptureDeviceTypeBuiltInDuoCamera

Answer 3

我想我已经弄明白了。我正在查看的文档是针对Xcode 9.您需要的是首先导入AVFoundation然后使用此函数：

class func defaultDevice(withDeviceType deviceType: AVCaptureDeviceType!, 
                                         mediaType: String!, 
                                          position: AVCaptureDevicePosition) -> AVCaptureDevice!

https://developer.apple.com/documentation/avfoundation/avcapturedevice/2361508-default?changes=latest_minor

例如：

let c = AVCaptureDevice.defaultDevice(withDeviceType: AVCaptureDeviceType.builtInTelephotCamer,
                                           mediaType: AVMediaTypeVideo,
                                            position: AVCaptureDevicePosition.front)

Answer 4

我只是想将我的项目转换为Swift4。这对我有用。

{{1}}

Answer 5

在将“ Swift语言版本”设置为“ Swift 3.3”时，我遇到了这个确切的错误。

将快速语言版本从“ 3.3”更改为“ 4.1”为我解决了这个问题。