如何切换IOS摄像头

import UIKit
import AVFoundation

class ViewController: UIViewController {
    var captureSession: AVCaptureSession?
    var currentCamera: AVCaptureDevice?
    var currentCameraInput: AVCaptureDeviceInput?
    var previewLayer: AVCaptureVideoPreviewLayer?

    override func viewDidLoad() {
        super.viewDidLoad()
        setupCaptureSession()
        setupPreviewLayer()
        startCaptureSession()
    }

    func setupCaptureSession() {
        captureSession = AVCaptureSession()
        captureSession?.sessionPreset = .photo

        guard let availableDevices = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: .video, position: .unspecified).devices else { return }
        for device in availableDevices {
            if device.position == .back {
                currentCamera = device
                break
            }
        }

        do {
            currentCameraInput = try AVCaptureDeviceInput(device: currentCamera!)
            captureSession?.addInput(currentCameraInput!)
        } catch {
            print(error.localizedDescription)
        }
    }

    func setupPreviewLayer() {
        previewLayer = AVCaptureVideoPreviewLayer(session: captureSession!)
        previewLayer?.videoGravity = .resizeAspectFill
        previewLayer?.frame = view.bounds
        view.layer.insertSublayer(previewLayer!, at: 0)
    }

    func startCaptureSession() {
        captureSession?.startRunning()
    }

    func switchCamera() {
        captureSession?.beginConfiguration()

        guard let newCameraInput = try? AVCaptureDeviceInput(device: getOppositeCamera()) else { return }

        captureSession?.removeInput(currentCameraInput!)

        if captureSession?.canAddInput(newCameraInput) ?? false {
            captureSession?.addInput(newCameraInput)
            currentCameraInput = newCameraInput
        } else {
            captureSession?.addInput(currentCameraInput!)
        }

        captureSession?.commitConfiguration()
    }

    func getOppositeCamera() -> AVCaptureDevice? {
        if currentCamera?.position == .back {
            return AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: .video, position: .front).devices.first
        } else {
            return AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: .video, position: .back).devices.first
        }
    }

    @IBAction func switchCameraButtonTapped(_ sender: UIButton) {
        switchCamera()
    }
}