AVCaptureDeviceRequestAccessBetter.swift

import AVFoundation

func cameraOn() {
  let status = AVCaptureDevice.authorizationStatus(for: .video)
  switch status {
    case .authroized:
      // has alraedy approved the privacy
      // open your camera(UIImagePickerController)
      break
    default:
      // remind and request the privacy again
      AVCaptureDevice.requestAccess(for: .video, completionHandler: { granted in
        if granted {
          // open your camera(UIImagePickerController)
        } else {
          // go settings to open the camera access
          requestCameraAccess()
        }
      }
      break
  }
}

func requestCameraAccess() {
  // remind users to open camera access in settings
  //....
  if let settingsUrl = URL(string: UIApplicationOpenSettingsURLString) {
    if UIApplication.shared.canOpenURL(settingsUrl) {
      if #available(iOS 10.0, *) {
        UIApplication.shared.open(settingsUrl, options: [:], completionHandler: { (success) in
          print("Open \(settingsUrl): \(success)")
        })
      } else {
        UIApplication.shared.openURL(settingsUrl)
      }
    }
  }
}