Switch 语句而不是大量的 if 语句答案

【问题标题】：Switch statement instead of a ton of if statementsSwitch 语句而不是大量的 if 语句
【发布时间】：2020-10-02 04:09:04
【问题描述】：

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，它将所有标识符与相应的字符串值一起保存：

    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"
}

还有我的委托方法：

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()
}

【问题讨论】：

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标签： ios swift if-statement switch-statement uilocalnotification

【解决方案1】：

初始化NotificationIdentifier 的enum 并使用如下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)")
    }
}

【讨论】：

【解决方案2】：

如果您只想打印出一个标识符，您可以使用单个打印语句：

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）。

【讨论】：

【解决方案3】：

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()
}

【讨论】：

【解决方案4】：

你可以像这样在 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()
}

【讨论】：