前提

iOS16以上
xxx.swift
import AVFoundation

struct XxxView: View {
    @State var showAlert = false;

    var body: some View {
        checkCamera()
        return ZStack(alignment: .bottom) {
          ...
        }
        .alert("カメラを使用できません", isPresented: $showAlert) {
            Button("Cancel") {}
            Button("設定") {
                guard let settingsURL = URL(string: UIApplication.openSettingsURLString ) else {
                    return
                }
                UIApplication.shared.open(settingsURL, options: [:], completionHandler: nil)
            }
        } message: {
            Text("iOSの設定でカメラへのアクセスを許可してください。")
        }
    }
    
    func checkCamera() {
        let status = AVCaptureDevice.authorizationStatus(for: AVMediaType.video)

        if status == AVAuthorizationStatus.authorized {
            // print("アクセス許可あり")
        } else if status == AVAuthorizationStatus.denied {
            // print("アクセス許可されていない")
            AVCaptureDevice.requestAccess(for: .video, completionHandler: { granted in
                if (granted == false) {
                    showAlert = true
                }
            })
        }
    }
}