ios - 变量显示为 nil - swift 4 IOS

Question

出于某种原因，我的变量 stringy 和 stringy 可以很好地打印到控制台，但是当我尝试将它们设置为标签时，它们显示为 nil。

我的目标是将字符串和 float 打印到应用程序 View Controller ，但这是行不通的。

我觉得跟viewdidload有关系，好像隐藏了全局变量。但是，如果我尝试在 viewdidload 之外设置标签，则会出现声明错误。

//  ViewController.swift
//  Intellicam
//

import UIKit
import AVKit
import Vision

class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {

    var stringy:String!
    var stringie:Float!

    override func viewDidLoad() {
        super.viewDidLoad()



        //here we start the camera

        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)

     //   let request = VNCoreMLModel(model: VNCoreMLModel, completionHandler: VNRequestCompletionHandler)
     //   VNImageRequestHandler(cgImage: <#T##CGImage#>, options: <#T##[VNImageOption : Any]#>)

        self.Labele.text = "Guess: \(stringy) + Certainty: \(stringie)"

    }

    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        //print("Camera was able to capture a frame:", Date())

        guard let pixelBuffer: CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else {return}

        guard let model = try? VNCoreMLModel(for: Resnet50().model) else {return}
        let request = VNCoreMLRequest(model: model){
            (finishedReq, err) in
            //print(finishedReq.results)

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

             guard let firstObservastion = results.first else {return}


            //print("Guess: \(firstObservastion.identifier) Certainty: \(firstObservastion.confidence)%")

            self.stringy = firstObservastion.identifier
            self.stringie = firstObservastion.confidence

            print(self.stringy)
            print(self.stringie)

        }

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

    @IBOutlet weak var Labele: UILabel!


}

Answer 1

首先，在您确定值(value)之前，切勿强行解包。在您的情况下， VNCoreModelRequest 可能会失败并且您的 both 变量将被取消分配，因此它会挑衅地使您的应用程序崩溃。还有一件事确保您对标签使用正确的命名约定。

您的问题是您没有根据获得的结果设置标签值。

解决这个问题

 var stringy:String? {
    didSet {
        DispatchQueue.main.async {
            self.Labele.text = self.stringy
        }
    }
}

或

        self.stringy = firstObservastion.identifier
        self.stringie = firstObservastion.confidence
        DispatchQueue.main.async {
             self.Labele.text = "Guess: \(stringy) + Certainty: \(stringie)"
         }