Question

我想请求一些权限，并希望返回false，除非已授予所有权限。我收到一个错误：＆＃34; void函数＆＃34;

中出现意外的非void返回值

但我在所有情况下都返回真/假，出了什么问题？

func requestPermissions () -> Bool {
    let types: UIRemoteNotificationType = [.alert, .badge, .sound]
    UIApplication.shared.registerForRemoteNotifications(matching: types)
    let center = UNUserNotificationCenter.current()

    AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeVideo, completionHandler: { (videoGranted: Bool) -> Void in
        if (videoGranted) {
            AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeAudio, completionHandler: { (audioGranted: Bool) -> Void in
                if (audioGranted) {
                    center.requestAuthorization(options: [.alert, .badge, .sound]) { (notificationGranted:Bool, error) -> Void in
                        if (notificationGranted) {
                            DispatchQueue.main.async {

                                return true
                                print("Video, audio & notifications granted")
                            }
                        } else {

                            return false
                            print("Rejected notifications")
                        }
                    }
                }else {

                    return false
                    print("Rejected audio")
                }
            })
        } else {

            return false
            print("Rejected video")
        }
    })
}

非常感谢任何帮助！谢谢。

替代答案：

func requestPermissionss (completion: ((Bool, Bool, Bool)->Void)?) {
    let types: UIRemoteNotificationType = [.alert, .badge, .sound]
    UIApplication.shared.registerForRemoteNotifications(matching: types)
    let center = UNUserNotificationCenter.current()

    AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeVideo, completionHandler: { (videoGranted: Bool) -> Void in
        AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeAudio, completionHandler: { (audioGranted: Bool) -> Void in
            center.requestAuthorization(options: [.alert, .badge, .sound]) { (notificationGranted:Bool, error) -> Void in
                completion?(videoGranted, audioGranted, notificationGranted)
            }
        })
    })
}

Answer 1

问题是，关闭return关键字内部与requestPermissions()函数的返回无关。它意味着从闭包返回，它实际上没有返回任何东西（因为-> Void部分）

您可以将带有三个bool参数的闭包传递给您的函数，如下所示：

func requestPermissions (completion: ((Bool, Bool, Bool)->Void)?) {
    let types: UIRemoteNotificationType = [.alert, .badge, .sound]
    UIApplication.shared.registerForRemoteNotifications(matching: types)
    let center = UNUserNotificationCenter.current()

    AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeVideo, completionHandler: { (videoGranted: Bool) -> Void in
        if (videoGranted) {
            AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeAudio, completionHandler: { (audioGranted: Bool) -> Void in
                if (audioGranted) {
                    center.requestAuthorization(options: [.alert, .badge, .sound]) { (notificationGranted:Bool, error) -> Void in
                        if (notificationGranted) {
                            completion?(true, true, true)
                        } else {
                            completion?(true, true, false)
                        }
                    }
                }else {
                    completion?(true, false, false)
                }
            })
        } else {
            completion?(false, false, false)
        }
    })
}

用法：

requestPermissions { (videoGranted, audioGranted, notificationsGranted) in
    print("video granted: \(videoGranted)")
    print("audio granted: \(audioGranted)")
    print("notifications granted: \(notificationsGranted)")
}

请注意，我也删除了DispatchQueue.main.async，因为这里没有任何意义。同样，return表示 return from the current scope ，而不是来自外部函数。

修改

需要注意的另一点是，如果视频权限遭到拒绝，您的代码就不会要求获得音频和通知权限。不确定它是否是故意的。如果事实上你需要独立请求所有这三件事，我认为这是你的情况，你应该使用类似的方法：

func requestPermissions() { let types: UIRemoteNotificationType = [.alert, .badge, .sound] UIApplication.shared.registerForRemoteNotifications(matching: types) self.requestVideo { videoGranted in print("video granted: \(videoGranted)") self.requestAudio { audioGranted in print("audio granted: \(audioGranted)") self.requestNotifications { notificationsGranted in print("notification granted: \(notificationsGranted)") } } } } func requestVideo (completion: ((Bool)->Void)?) { AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeVideo, completionHandler: { (videoGranted: Bool) -> Void in completion?(videoGranted) }) } func requestAudio (completion: ((Bool)->Void)?) { AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeAudio, completionHandler: { (audioGranted: Bool) -> Void in completion?(audioGranted) }) } func requestNotifications (completion: ((Bool)->Void)?) { UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { (notificationGranted:Bool, error) -> Void in completion?(notificationGranted) } }

基本上，只要您完成上一个操作，就会立即要求下一个操作，并且无论先前请求的选择是什么，都会独立请求下一个操作。

Answer 2

你试图在completionHandler块中返回Bool值，这是返回类型void，你可能显然知道什么都不应该被返回!!!

这就是您遇到此错误的原因“void函数中出现意外的非空返回值”

在嵌套函数中返回bool

2 个答案: