如何在Swift中检查launchOptions？

Question

我在这里碰到了一些麻烦 - 我正在尝试检测我的应用是否是从本地通知启动的。但是我的所有代码都出现了故障。

func application(application: UIApplication!, didFinishLaunchingWithOptions launchOptions: NSDictionary!) -> Bool {
    var firstWay = launchOptions.objectForKey(UIApplicationLaunchOptionsLocalNotificationKey)
    var secondWay = launchOptions[UIApplicationLaunchOptionsLocalNotificationKey]
    return true
}

这两个操作都会显示失败信息

"unexpectedly found nil while unwrapping an Optional value"

我相信我在这里做了一些非常基础的错误。有什么指针吗？

- bitops

Answer 1

您正在解包 launchOptions 字典，但它经常是 nil。尝试解包为 nil 值将导致崩溃，因此在使用尾随感叹号进行解包之前，您需要检查它是否为 nil。正确的代码如下：

if let options = launchOptions {
    // use the unwrapped `options` variable here
} else {
    // `launchOptions` was `nil`, handle it accordingly
}

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool {
    if let options = launchOptions {
       // Do your checking on options here
    }

    return true
}

- bjtitus

Answer 2

最清晰的方法：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    if let notification:UILocalNotification = launchOptions?[UIApplicationLaunchOptionsLocalNotificationKey] as? UILocalNotification {
        //do stuff with notification
    }
    return true
}

- Jesse Hull

Answer 3

您也可以这样做：

let notification = launchOptions?[UIApplicationLaunchOptionsLocalNotificationKey] as! UILocalNotification!
if (notification != nil) {
    // Do your stuff with notification
}

- hufeng03

---

如果通知为nil，甚至在到达测试之前就会崩溃。你不应该写像"as! UILocalNotification!"这样的东西。 - Frederic Adda