switch 语句而不是大量的 if 语句

Question

我目前正在处理通知并想打印出一个标识符。如何用一个开关替换所有 if 语句？

这是我的枚举，它使所有标识符都具有相应的字符串值：

    enum NotificationIdentifier:String {
    case local = "Local Notification"
    case localWithAction = "Local Notification with Action"
    case localWithContent = "Local Notification with Content"
    case pushWithAPNs = "Push Notification with  APNs"
    case pushWithFirebase = "Push Notification with Firebase"
    case pushWithContent = "Push Notification with Content"
}

我的委托方法：

func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {

    if response.notification.request.identifier == NotificationIdentifier.local.rawValue {
        print("Handling notification with the \(NotificationIdentifier.local.rawValue)")
    } else if response.notification.request.identifier == NotificationIdentifier.localWithAction.rawValue {
        print("Handling notification with the \(NotificationIdentifier.localWithAction.rawValue)")
    } else if response.notification.request.identifier == NotificationIdentifier.localWithContent.rawValue {
        print("Handling notification with the \(NotificationIdentifier.localWithContent.rawValue)")
    } else if response.notification.request.identifier == NotificationIdentifier.pushWithAPNs.rawValue {
        print("Handling notification with the \(NotificationIdentifier.pushWithAPNs.rawValue)")
    } else if response.notification.request.identifier == NotificationIdentifier.pushWithFirebase.rawValue {
        print("Handling notification with the \(NotificationIdentifier.pushWithFirebase.rawValue)")
    } else {
        print("Handling notification with the \(NotificationIdentifier.pushWithContent.rawValue)")
    }

    completionHandler()
}

Answer 1

您可以像这样在 Enum 上使用 switch case：

func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
    switch response.notification.request.identifier {
        case .local:
            print("local")
        case .localWithAction:
            print("localWithAction")
        case .localWithAction:
            print("localWithAction")
        case .localWithContent:
            print("localWithContent")
        case .pushWithAPNs:
            print("pushWithAPNs")
        case .pushWithFirebase:
            print("pushWithFirebase")
    default:
        print("pushWithContent")
    }
    completionHandler()
}

Answer 2

你可以避免这样的 switch 和 if else 语句......你得到 NotificationIdentifier 这段代码的情况......

func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {


    if let notificationIdentifier =   NotificationIdentifier(rawValue: response.notification.request.identifier) {

        print("Handling notification with the \(notificationIdentifier.rawValue)")

        switch notificationIdentifier {
        case .local:
            print("Handle local")
        case .localWithAction:
            print("Handle localWithAction")
        case .localWithContent:
            print("Handle localWithContent")
        case .pushWithAPNs:
            print("Handle pushWithAPNs")
        case .pushWithFirebase:
            print("Handle pushWithFirebase")
        case .pushWithContent:
            print("Handle pushWithContent")

        }


    } else {
        print("cant convert to NotificationIdentifier")
    }

    completionHandler()
}

Answer 3

如果您只想打印出一个标识符，您可以使用一个打印语句：

let notificationIdentifier = NotificationIdentifier.init(rawValue: response.notification.request.identifier) ?? .pushWithContent)
print("Handling notification with the \(notificationIdentifier.rawValue)")

这也将涵盖默认值（例如 .pushWithContent）。

Answer 4

初始化 NotificationIdentifier 的 enum 并像下面这样使用 switch case:

func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
    guard let notificationIdentifier = NotificationIdentifier(rawValue: response.notification.request.identifier) else { return }
    switch notificationIdentifier {
    case .local:
    print("Handling notification with the \(NotificationIdentifier.local.rawValue)")
    case .localWithAction:
    print("Handling notification with the \(NotificationIdentifier.localWithAction.rawValue)")
    case .localWithContent:
    print("Handling notification with the \(NotificationIdentifier.localWithContent.rawValue)")
    case .pushWithAPNs:
    print("Handling notification with the \(NotificationIdentifier.pushWithAPNs.rawValue)")
    case .pushWithFirebase:
    print("Handling notification with the \(NotificationIdentifier.pushWithFirebase.rawValue)")
    case .pushWithContent:
    print("Handling notification with the \(NotificationIdentifier.pushWithContent.rawValue)")
    }
}

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