UIViewにカメラの映像を表示

細かい所は全然分かってないけど、とりあえずUIView（ここではcameraViewという名前)にカメラの映像を表示するプログラム

ViewController.swift

import UIKit
import AVFoundation

class ViewController: UIViewController{

    @IBOutlet weak var cameraView: UIView!
    var captureSesssion: AVCaptureSession!
    var stillImageOutput: AVCapturePhotoOutput?
    var previewLayer: AVCaptureVideoPreviewLayer?
    override func viewWillAppear(_ animated: Bool) {

        captureSesssion = AVCaptureSession()
        stillImageOutput = AVCapturePhotoOutput()

        captureSesssion.sessionPreset = AVCaptureSessionPreset1920x1080 // 解像度の設定

        let device = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)

        do {
            let input = try AVCaptureDeviceInput(device: device)

            // 入力
            if (captureSesssion.canAddInput(input)) {
                captureSesssion.addInput(input)

                // 出力
                if (captureSesssion.canAddOutput(stillImageOutput)) {
                    captureSesssion.addOutput(stillImageOutput)
                    captureSesssion.startRunning() // カメラ起動

                    previewLayer = AVCaptureVideoPreviewLayer(session: captureSesssion)
                    previewLayer?.videoGravity = AVLayerVideoGravityResizeAspect // アスペクトフィット
                    previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.portrait // カメラの向き

                    cameraView.layer.addSublayer(previewLayer!)

                    // ビューのサイズの調整
                    previewLayer?.position = CGPoint(x: self.cameraView.frame.width/2, y: self.cameraView.frame.height/2)
                    previewLayer?.bounds = cameraView.frame
                }
            }
        }
        catch {
            print(error)
        }
    }
}

※追記
Info.plistにPrivacy-Camera Usage DescriptionのKeyを追加