Swiftでカメラキャプチャーするための最小コード

準備

Info.plist に以下の設定を追加。

    <key>NSCameraUsageDescription</key>
    <string>[カメラ使用に関する説明]</string>

コード

import UIKit
import AVFoundation

class CaptureViewController: UIViewController {

    private let previewLayer: AVCaptureVideoPreviewLayer = {
        let previewLayer = AVCaptureVideoPreviewLayer()
        previewLayer.videoGravity = .resizeAspectFill
        return previewLayer
    }()

    init() {
        super.init(nibName: nil, bundle: nil)

        let session = AVCaptureSession()
        previewLayer.session = session

        if let device = AVCaptureDevice.default(for: .video),
           let input = try? AVCaptureDeviceInput(device: device),
           session.canAddInput(input) {
            session.addInput(input)
        }

        let output = AVCaptureVideoDataOutput()
        output.setSampleBufferDelegate(self, queue: .global())
        if session.canAddOutput(output) {
            session.addOutput(output)
            output.connection(with: .video)?.videoOrientation = .portrait
        }

        session.startRunning()
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.layer.addSublayer(previewLayer)
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        previewLayer.frame = CGRect(origin: .zero, size: view.bounds.size)
    }

}

extension CaptureViewController: AVCaptureVideoDataOutputSampleBufferDelegate {

    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        // sampleBufferを処理する
    }

}

環境

Xcode 12.2

Apple Swift version 5.3.1 (swiftlang-1200.0.41 clang-1200.0.32.8)
Target: x86_64-apple-darwin19.6.0