'ErrorType' 不能转换为 'NSError'

Question

我在使用 Google Analytics 时遇到了错误：

'ErrorType' 不能转换为 'NSError'；你的意思是用'as！' 强制沮丧？

当我尝试调用 2 次 createScreenView 时会发生这种情况

我这样做：

    override func viewDidLoad() {


        let tracker = GAI.sharedInstance().defaultTracker
        tracker.set(kGAIScreenName, value: "Demande Gratuite")

        var builder = GAIDictionaryBuilder.createScreenView().build() as! [NSObject : AnyObject]
        tracker.send(builder)
...
}

    @IBAction func Valider(sender: AnyObject) {
        ...
        let trackerv = GAI.sharedInstance().defaultTracker
        trackerv.set(kGAIScreenName, value: "Demande Envoyé")

        var builder = GAIDictionaryBuilder.createScreenView().build() as! [NSObject : AnyObject]
        trackerv.send(builder)


        let eventTracker: NSObject = GAIDictionaryBuilder.createItemWithTransactionId(
            "1",
            name: "test",
            sku: nil,
            category: "IOS",
            price: 1,
            quantity: 1,
            currencyCode: nil).build()
        trackerv.send(eventTracker as! [NSObject : AnyObject])
    }

错误所在的函数：

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
    // The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
    // Create the coordinator and store
    let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("SingleViewCoreData.sqlite")
    var failureReason = "There was an error creating or loading the application's saved data."
    do {
        try coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
    } catch {
        // Report any error we got.
        var dict = [String: AnyObject]()
        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
        dict[NSLocalizedFailureReasonErrorKey] = failureReason

        dict[NSUnderlyingErrorKey] = error as NSError
        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
        // Replace this with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
        abort()
    }

    return coordinator
}()

这里还有一个问题：

let tracker = GAI.sharedInstance().defaultTracker
tracker.set(kGAIScreenName, value: "Mentions Légales")

var builder = GAIDictionaryBuilder.createScreenView().build() as! [NSObject : AnyObject]
tracker.send(builder)

从 'NSMutableDictionary!' 强制转换到“[NSObject：AnyObject]” 总是成功；你的意思是用'as'吗？

与

变量“builder”从未发生变异；考虑改为“让” 常数

Answer 1

错误消息会告诉您问题并提出解决方案。 catch 块中的常量error 是ErrorType 类型，您想将其转换为NSError，这种转换可能不会成功。因此，您不能使用常规的 as 运算符，该运算符仅用于编译器可以判断的强制转换总是成功的。相反，您需要使用 as! 强制转换或使用 as? 进行安全转换。

catch {
        // Report any error we got.
        var dict = [String: AnyObject]()
        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
        dict[NSLocalizedFailureReasonErrorKey] = failureReason

        if let underlyingError = error as? NSError {
            dict[NSUnderlyingErrorKey] = underlyingError
        }
        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
        // Replace this with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
        abort()
    }

对于您的第二个问题，您遇到了相反的问题。您正在使用 as! 运算符进行编译器知道将始终有效的强制转换。您应该只使用普通的 as 运算符。第三个问题是您要声明一个变量 (var)，其值永远不会改变。在这些情况下，最好使用常量 (let)。

let builder = GAIDictionaryBuilder.createScreenView().build() as [NSObject : AnyObject]

Answer 2

对我来说，在同一个项目中使用 AVFoundation 和 Core Data 时也会发生这种情况。

摆脱错误：

'ErrorType' 不能转换为 'NSError'；你的意思是用'as！'强制沮丧？

或警告：

从 'ErrorType' 到 'NSError' 的条件转换总是成功

从 'ErrorType' 强制转换为 'NSError' 总是成功的；你的意思是用'as'吗？

我这样做了：

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
    // The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
    // Create the coordinator and store
    let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("MY_APP_NAME.sqlite")
    var failureReason = "There was an error creating or loading the application's saved data."
    do {
        try coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
    } catch let error as NSError {
        // Report any error we got.
        var dict = [String: AnyObject]()
        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
        dict[NSLocalizedFailureReasonErrorKey] = failureReason

        dict[NSUnderlyingErrorKey] = error
        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
        // Replace this with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
        abort()
    } catch {
        // dummy
    }
    
    return coordinator
}()

希望这会有所帮助:)