语言：Swift 4.2。

问题是iOS 13.0对我自iOS 12.0起使用的相同代码的要求。与许多人在更新Xcode之后相同的问题。 先前安装的macOS Catalina和Xcode 11.2。

结果：“ imageBuffer”仅在iOS 13.0或更高版本中可用。

代码（课程前带有“ @available”）

import UIKit
import AVKit
import Vision

@available(iOS 13.0,*)
class VideoViewController: UIViewController,AVCaptureVideoDataOutputSampleBufferDelegate
{
    let identifierLabel: UILabel = {
        let label = UILabel()
        label.backgroundColor = .white
        label.textAlignment = .center
        label.translatesAutoresizingMaskintoConstraints = false
        return label
    }()

    override func viewDidLoad()
    {
        super.viewDidLoad()
        let captureSession = AVCaptureSession()
        captureSession.sessionPreset = .photo

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

        let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        view.layer.addSublayer(previewLayer)
        previewLayer.frame = view.frame

        let dataOutput = AVCaptureVideoDataOutput()
        dataOutput.setSampleBufferDelegate(self,queue: DispatchQueue(label: "videoQueue"))
        captureSession.addOutput(dataOutput)
        setupIdentifierConfidenceLabel()
    }

    fileprivate func setupIdentifierConfidenceLabel() {
        view.addSubview(identifierLabel)
        identifierLabel.bottomAnchor.constraint(equalTo: view.bottomAnchor,constant: -32).isactive = true
        identifierLabel.leftAnchor.constraint(equalTo: view.leftAnchor).isactive = true
        identifierLabel.rightAnchor.constraint(equalTo: view.rightAnchor).isactive = true
        identifierLabel.heightAnchor.constraint(equalToConstant: 50).isactive = true
    }

    func captureOutput(_ output: avcaptureoutput,didOutput sampleBuffer: CMSampleBuffer,from connection: AVCaptureConnection) {

        //connection.videoOrientation = AVCaptureVideoOrientation.landscapeleft
        let pixelBuffer: CVPixelBuffer = sampleBuffer.imageBuffer!
        let ciimage : CIImage = CIImage(cvPixelBuffer: pixelBuffer)
        let _ : UIImage = self.convert(cmage: ciimage)

        guard let model = try? VNCoreMLModel(for: Faceclassifier2().model) else { return }
        let request = VNCoreMLRequest(model: model)
        { (finishedReq,err) in

            guard let results = finishedReq.results as? [VNClassificationObservation] else { return }
            guard let firstObservation = results.first else { return }

            print(firstObservation.identifier,firstObservation.confidence)

            DispatchQueue.main.async {
                self.identifierLabel.text = "\(firstObservation.identifier) \(firstObservation.confidence * 100)"
            }

        }

        try? VNImageRequestHandler(cvPixelBuffer: pixelBuffer,options: [:]).perform([request])
    }

    // Convert CIImage to CGImage
    func convert(cmage:CIImage) -> UIImage {
        let context:CIContext = CIContext.init(options: nil)
        let cgImage:CGImage = context.createCGImage(cmage,from: cmage.extent)!
        let image:UIImage = UIImage.init(cgImage: cgImage)
        return image
    }
}

问题：是否可以在没有@available的情况下使其在iOS 12.0上运行？ 原因是大多数人仍然根本无法购买新iPhone和安装iOS 13.0。

P.S：Apple更新不再让我们的生活变得更轻松。