Error: Type 'String!' has no member 'video'

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()
    }
}

I get the error in this line at (for: .video ):

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

Answer 1

用AVMediaTypeVideo替换AVMediaType.video对我有用。

Answer 2

The method

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

Accepts a DeviceType, which can be:

AVCaptureDeviceTypeBuiltInMicrophone
AVCaptureDeviceTypeBuiltInWideAngleCamera
AVCaptureDeviceTypeBuiltInTelephotoCamera
AVCaptureDeviceTypeBuiltInDualCamera
AVCaptureDeviceTypeBuiltInDuoCamera

Answer 3

I think I have figured it out. The documentation I was looking at was for Xcode 9. What you need is first to import AVFoundation and then use this function:

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

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

For example:

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

Answer 4

I'm just trying to convert my project to Swift4. This works for me.

device = AVCaptureDevice.default(for: AVMediaType.video)

Answer 5

I got this exact error when building with "Swift language Version" set to "Swift 3.3".

Changing the swift language version from "3.3" to "4.1" solved the issue for me.