致命错误：无法解包Optional.None使用Swift和Parse时

Question

我已经按照这个将你的swift应用程序连接到Parse.com教程：http://ios-blog.co.uk/tutorials/connect-your-swift-application-to-parse-com/并且效果很好。本教程仅向您介绍如何在Parse.com服务上放置数据。所以我做了一些关于如何检索数据的研究。

在第一篇教程中，它表示将数据添加到Parse中，如下所示：

    Parse.setApplicationId("your_application_key", clientKey: "your_client_key")

    var object = PFObject(className: "testDataClass")
    object.addObject("iOSBlog", forKey: "websiteUrl")
    object.addObject("Five", forKey: "websiteRating")
    object.save()

在第二篇教程中，由Parse团队编写（http://blog.parse.com/2014/06/06/building-apps-with-parse-and-swift/）它写的是这样写的：

var gameScore = PFObject(className: "GameScore")
gameScore.setObject(1337, forKey: "score")
gameScore.setObject("Sean Plott", forKey: "playerName")
gameScore.saveInBackgroundWithBlock { 
    (success: Bool!, error: NSError!) -> Void in
    if success {
        NSLog("Object created with id: \(gameScore.objectId)")
    } else {
        NSLog("%@", error)
    }
}

然后要检索它，请使用以下代码：

 var query = PFQuery(className: "GameScore")
 query.getObjectInBackgroundWithId(gameScore.objectId) {
 (scoreAgain: PFObject!, error: NSError!) -> Void in
     if !error {
        NSLog("%@", scoreAgain.objectForKey("playerName") as NSString)
     } else {
        NSLog("%@", error)
    }
}

但是，当我使用官方解析代码时，我收到以下错误：

fatal error: Can't unwrap Optional.None
(lldb) 

所有这些事情几乎发生在Xcode的每个窗格中：

有人可以告诉我有什么问题以及如何解决这个问题？我对Xcode和Swift相对较新，所以我非常感谢外行人的条款回答。

编辑这是appDelegate.swift函数

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool {

    // Connect to Parse using the keys provided

    Parse.setApplicationId("xxx", clientKey: "xxx")

    // Store Data to Parse

    var gameScore = PFObject(className: "GameScore")
    gameScore.setObject(1337, forKey: "score")
    gameScore.setObject("Sean Plott", forKey: "playerName")
    gameScore.saveInBackgroundWithBlock {
        (success: Bool!, error: NSError!) -> Void in
        if success {
            NSLog("Object created with id: \(gameScore.objectId)")
        } else {
            NSLog("%@", error)
        }
    }

    var query = PFQuery(className: "GameScore")
    query.getObjectInBackgroundWithId(gameScore.objectId) {
        (scoreAgain: PFObject!, error: NSError!) -> Void in
        if !error {
            NSLog("%@", scoreAgain.objectForKey("playerName") as NSString)
        } else {
            NSLog("%@", error)
        }
    }



    // Override point for customization after application launch.
    return true
}

非常感谢。

为用户添加了新代码以查看：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool {

    // Connect to Parse using the keys provided

    Parse.setApplicationId("xxxx", clientKey: "xxxx")

    // Store Data to Parse

    var gameScore = PFObject(className: "GameScore")
    gameScore.setObject(1337, forKey: "score")
    gameScore.setObject("Sean Plott", forKey: "playerName")
    gameScore.saveInBackgroundWithBlock {
        (success: Bool!, error: NSError!) -> Void in
        if (success ?? false) {
            NSLog("Object created with id: \(gameScore.objectId)")
        } else {
            NSLog("%@", error)
        }
    }

    var query = PFQuery(className: "GameScore")
    query.getObjectInBackgroundWithId(gameScore.objectId) {
        (scoreAgain: PFObject!, error: NSError!) -> Void in
        if error == nil {
            NSLog("%@", scoreAgain.objectForKey("playerName") as NSString)
        } else {
            NSLog("%@", error)
        }
    }



    // Override point for customization after application launch.
    return true
}

Answer 1

这个Parse示例是在Swift处于Beta版时于6月份编写​​的。斯威夫特继续发展，所以他们正在做的一些事情在斯威夫特不再合法。

首先，您无法再使用error检查可选变量nil是否为if !error。相反，您必须明确检查nil，如下所示：if error == nil。

其次，success被声明为隐式解包的可选项。使用true检查if success是否有效无效。您可以执行if success == true但如果success为nil，则会崩溃。相反，你可以做if (success ?? false)。如果Bool有值，则使用 nil coalescing operator 安全地展开可选false，如果Bool为nil，则使用if。无论哪种方式，Bool只有在true为{{1}}时才会成功。