APPDelegate 中的 openURL 转换错误 NSString -> String (Swift & iOS8)

Question

我目前正在开发一个集成 Facebook 的 iOS 应用程序，但在使用 Swift 进行调查时遇到了一些问题（使用 ObjC 我没有问题）。

问题是，当来自另一个 APP（在本例中为 WebBrowser 中的 FB）时，这是在 appDelegate 中执行的方法：

func application(
    application: UIApplication,
    openURL url: NSURL,
    sourceApplication: NSString,
    annotation: AnyObject)
    -> Bool { 
       let appString : String = sourceApplication as String // Try to convert format => EXCEPTION
       let appString : String = String(sourceApplication)   // 'SSS' Suggestion: EXCEPTION
       println(sourceApplication) // Try to print the value => EXCEPTION
       return FBAppCall.handleOpenURL(url, sourceApplication:sourceApplication,
            withSession:session) // With Parse => EXCEPTION
}

在该方法中，我在使用“sourceApplication”参数时遇到了真正的问题。我尝试使用它，我得到一个例外。我尝试转换它，另一个异常......甚至无法记录它的值，因为它在访问它的值时崩溃。将函数签名中的参数类型更改为 String 无效。

这是我得到的错误：

EXEC_BAD_ACCESS

我一直在追查，直到我读到这绝对是一个有价值的提示：

ObjectiveC.NSString.__conversion (ObjectiveC.NSString)() -> Swift.String

会不会是 iOS8 的错误？ 你们中有人遇到过这个问题和/或知道如何解决吗？

Answer 1

你犯了两个错误：

1. 来自app Delegate 的函数声明是func application(application: UIApplication!, openURL url: NSURL!, sourceApplication: String!, annotation: AnyObject!) -> Bool：sourceApplication 是一个可选的String 值而不是NSString。

2. 由于 sourceApplication 是可选的，它可能会返回 nil 值（在您的情况下返回 nil）。将 nil 类型转换为 String 是不安全的，因此会崩溃。

解决方案：

1. 您的情况不需要类型转换，因为返回值是 String 类型
2. 使用可选的表单类型转换运算符 as? 来安全地进行类型转换，即

if let appString = sourceApplication { println(appString as? String) }

Answer 2

这对我有用（使用 FacebookSDK）：

func application(application: UIApplication, openURL url: NSURL, sourceApplication: NSString?, annotation: AnyObject) -> Bool {
    var wasHandled:Bool = FBAppCall.handleOpenURL(url, sourceApplication: sourceApplication)
    return wasHandled
}

Answer 3

我在操场上看不到这个。正如您所建议的，可能是 iOS 8 错误 但是为了尝试，你可以试试吗

let appString : String = String(sourceApplication)

Answer 4

对于 FB Messenger，这是我为在 AppDelegate 中获得更好处理所做的工作。大多数想法直接取自 FB IOS documentation 并移植到 Swift。

为什么我觉得我应该写一个额外的回复？我有一些使用 Swift 的经验，但我觉得我浪费了足够多的时间来尝试获取正确的代码集来做我想做的事需要 FB Messenger。希望原始代码对某些人有用，只是为了整合很多点点滴滴并节省一些时间。

注意：这不包括您想要/需要的所有 AppDelegate 生命周期方法，但希望这是一个良好的开端

@UIApplicationMain class AppDelegate: UIResponder, UIApplicationDelegate, FBSDKMessengerURLHandlerDelegate {

var window: UIWindow?
var messengerUrlHandler: FBSDKMessengerURLHandler?
var cancelContext : FBSDKMessengerURLHandlerCancelContext?
var composerContext : FBSDKMessengerURLHandlerOpenFromComposerContext?
var replyContext: FBSDKMessengerURLHandlerReplyContext?

// Facebook Messenger
enum MessengerShareMode : Int {
    case MessengerShareModeCancel
    case MessengerShareModeSend
    case MessengerShareModeComposer
    case MessengerShareModeReply
}

// shareMode holds state indicating which flow the user is in.
// Return the corresponding FBSDKMessengerContext based on that state.
var shareMode : MessengerShareMode?

/*
* Initialize the FB messenger handler and set self as the delegate.
*/
func application(application: UIApplication, willFinishLaunchingWithOptions launchOptions: [NSObject : AnyObject]?) -> Bool {
    YARAppearance.setAppearance()

    let rootController = TabBarController()
    self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
    self.window!.rootViewController = rootController
    self.window!.makeKeyAndVisible()

    // Facebook messenger handling
    self.messengerUrlHandler = FBSDKMessengerURLHandler()
    if (self.messengerUrlHandler != nil) {
        self.messengerUrlHandler!.delegate = self
    }
    return true
}

/*
* Handle the cancel context flow.
*/
func messengerURLHandler(messengerURLHandler: FBSDKMessengerURLHandler!,
    didHandleCancelWithContext context: FBSDKMessengerURLHandlerCancelContext!) {
        self.cancelContext = context
        self.shareMode = .MessengerShareModeCancel
}

/*
* When people enter your app through the composer in Messenger,
* this delegate function will be called.
*/
func messengerURLHandler(messengerURLHandler: FBSDKMessengerURLHandler!,
    didHandleOpenFromComposerWithContext context: FBSDKMessengerURLHandlerOpenFromComposerContext!) {
        self.composerContext = context
        self.shareMode = .MessengerShareModeComposer
}

/*
* When people enter your app through the "Reply" button on content
* this delegate function will be called.
*/
func messengerURLHandler(messengerURLHandler: FBSDKMessengerURLHandler!,
    didHandleReplyWithContext context: FBSDKMessengerURLHandlerReplyContext!) {
    self.replyContext = context
    self.shareMode = .MessengerShareModeReply
}

/*
* Handle URL calls from external applications, particularly Messenger
*/
func application(application: UIApplication, openURL url: NSURL, sourceApplication: String?, annotation: AnyObject) -> Bool {
    let wasHandled:Bool = self.messengerUrlHandler!.openURL(url, sourceApplication: sourceApplication)
    return wasHandled
}

/*
* A way to access the context objects elsewhere
*/
func getContextForShareMode() -> FBSDKMessengerContext? {
    // shareMode holds state indicating which flow the user is in.
    // Return the corresponding FBSDKMessengerContext based on that state.
    if (shareMode == .MessengerShareModeSend) {
        // Force a send flow by returning a broadcast context.
        return FBSDKMessengerBroadcastContext()

    } else if (shareMode == .MessengerShareModeComposer) {
        // Force the composer flow by returning the composer context.
        return self.composerContext!

    } else if (shareMode == .MessengerShareModeReply) {
        // Force the reply flow by returning the reply context.
        return self.replyContext!
    }
    return nil
}
}