Question

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

这是我的枚举，它保留所有具有相应字符串值的标识符：

    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

初始化enum中的NotificationIdentifier，并使用如下所示的切换用例：

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)")
    }
}

Answer 2

您可以像这样在Enum上使用切换用例：

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 3

您可以避免切换，如果出现其他类似这样的语句，则您可以在这段代码中得到#include <pthread.h> #include <stdio.h> #include <stdlib.h> struct Params { char* ch; int num; }; void* print_char(void* th_param) { int i; struct Params* par = (struct Params*)th_param; for(i=0; i<par->num; i++) { printf("%s", par->ch); } return NULL; } int main() { struct Params* p1 = malloc(sizeof(struct Params)); p1->ch = "a"; p1->num = 5; struct Params* p2 = malloc(sizeof(struct Params)); p2->ch = "b"; p2->num = 10; pthread_t th_id; pthread_create(&th_id, NULL, &print_char, p1); pthread_t th_id2; pthread_create(&th_id2, NULL, &print_char, p2); fflush(stdout); while(1) {;} return 0; }的情况……

NotificationIdentifier

Answer 4

如果您只想打印出一个标识符，则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)")

这还将覆盖默认值（例如.pushWithContent）。

切换语句而不是大量的if语句

4 个答案: