等待iOS

Question

我有一个与我的代码相关的问题：

func isNotificationsEnabled()->Bool{
    var isNotificationEnabled = false
    center.getNotificationSettings() { (settings) in
        switch settings.soundSetting{
        case .enabled:
            isNotificationEnabled = true
           break
        case .disabled:
             isNotificationEnabled = false
             break

        case .notSupported:
            isNotificationEnabled = false
             break
        }
    }

     return isNotificationEnabled
}

此函数在center.getNotificationSettings()返回结果之前返回结果。有没有办法等待center.getNotificationSettings()的结果并同步此功能？

Answer 1

您正在寻找的是iOS中的完成块， 试试这个，

func isNotificationsEnabled(completion:@escaping (Bool)->Swift.Void){
        var isNotificationEnabled = false
        center.getNotificationSettings() { (settings) in
            switch settings.soundSetting{
            case .enabled:
                isNotificationEnabled = true
                completion(isNotificationEnabled)
                break
            case .disabled:
                isNotificationEnabled = false
                completion(isNotificationEnabled)
                break

            case .notSupported:
                isNotificationEnabled = false
                completion(isNotificationEnabled)
                break
            }
        }
    }

用法，

isNotificationsEnabled { (isNotificationEnabled) in
    debugPrint(isNotificationEnabled)           
}

Answer 2

这是一个使用完成块的示例，它已经缩减但功能与您的代码相同：

func isNotificationsEnabled(completion:@escaping (Bool)->() ) {
    center.getNotificationSettings() { (settings) in
        switch settings.soundSetting {
        case .enabled:
            completion(true)

        default:
            completion(false)
        }
    }
}

可以更加简化为必要：

func isNotificationsEnabled(completion:@escaping (Bool)->() ) {
    center.getNotificationSettings() { (settings) in
        completion (settings.soundSetting == .enabled)
    }
}

由于只有.enabled案例返回true，因此在所有其他情况下都会使用default返回false。顺便说一句：在Swift中break不需要语句。

并称之为：

isNotificationsEnabled { success in
    if success {
        print("is enabled")
    } else {
        print("is disabled")
    }
}

Answer 3

仅供参考，您可以进一步简化：

func isNotificationsEnabled(completionHandler: @escaping (Bool) -> Void) {
    center.getNotificationSettings { settings in
        completionHandler(settings.soundSetting == .enabled)
    }
}

正如其他人指出的那样，它被调用为：

isNotificationsEnabled { enabled in
    if enabled {
        print("is enabled")
    } else {
        print("is not enabled")
    }
}

Answer 4

添加完成处理程序！

func isNotificationsEnabled(completion: (Bool) -> ())->Bool{
    var isNotificationEnabled = false
    center.getNotificationSettings() { (settings) in
        switch settings.soundSetting{
        case .enabled:
            isNotificationEnabled = true
           break
        case .disabled:
             isNotificationEnabled = false
             break

        case .notSupported:
            isNotificationEnabled = false
             break
        }
    }

     return isNotificationEnabled
     completion(isNotificationEnabled)
}

然后叫它

isNotificationEnabled() { isNotificationsEnabled in
   print(isNotificationsEnabled)
}