未捕获的异常：-[UIKeyboardTaskQueue waitUntilAllTask​​sAreFinished]中的断言失败

Question

我正在使用Swift 2.3。 我正在构建包含Firebase Auth的应用程序。

现在，我想发送SendResetPassword，然后显示alertController，其标题和消息根据所键入的电子邮件而改变。 我试图在点击发送按钮时在ViewController中呈现AlertController：

@IBAction func sendButtonTapped(sender: UIButton) {

        if txtEmail.text == "" {
            let alertController = UIAlertController(title: "Error", message: "Please enter an e-mail", preferredStyle: .Alert)
            let defaultAction = UIAlertAction(title: "Ok", style: .Cancel, handler: nil)
            alertController.addAction(defaultAction)

            self.presentViewController(alertController, animated: true, completion: nil)
        } else {

            FIRAuth.auth()?.sendPasswordResetWithEmail(txtEmail.text!, completion: { (error) in
                var title = ""
                var message = ""

                if error != nil {
                    title = "Error"
                    message = (error?.localizedDescription)!
                } else {
                    title = "Success!"
                    message = "Password reset email sent."
                    self.txtEmail.text = ""
                }


                let alertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
                let defaultAction = UIAlertAction(title: "Ok", style: .Cancel, handler: nil)
                alertController.addAction(defaultAction)

                self.presentViewController(alertController, animated: true, completion: nil)
            })
        }

    }

结果导致了一个例外。 试图放置断点，并且一切正常，直到出现AlertController为止。 在控制台窗口中，我有以下内容：

2016-10-15 00:13:44.657 Doner[51377:4529688] *** Assertion failure in -[UIKeyboardTaskQueue waitUntilAllTasksAreFinished], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit_Sim/UIKit-3512.60.7/Keyboard/UIKeyboardTaskQueue.m:386
2016-10-15 00:13:44.662 Doner[51377:4529688] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UIKeyboardTaskQueue waitUntilAllTasksAreFinished] may only be called from the main thread.'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000010b221d85 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010d243deb objc_exception_throw + 48
    2   CoreFoundation                      0x000000010b221bea +[NSException raise:format:arguments:] + 106
    3   Foundation                          0x000000010b673d5a -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 198
    4   UIKit                               0x000000010c6c8a73 -[UIKeyboardTaskQueue waitUntilAllTasksAreFinished] + 165
    5   UIKit                               0x000000010bf36bc4 -[UIKeyboardImpl prepareForSelectionChange] + 100
    6   UIKit                               0x000000010be0e149 -[UIFieldEditor setAttributedText:andSetCaretSelectionAfterText:] + 146
    7   UIKit                               0x000000010be0de2c -[UIFieldEditor setText:andSetCaretSelectionAfterText:] + 172
    8   UIKit                               0x000000010c693ece -[UITextField setText:] + 344
    9   Doner                               0x000000010960fde4 _TFFC5Doner20ForgotViewController16sendButtonTappedFCSo8UIButtonT_U_FGSqCSo7NSError_T_ + 772
    10  Doner                               0x000000010960c5a7 _TTRXFo_oGSqCSo7NSError__dT__XFo_iGSqS___iT__ + 23
    11  Doner                               0x000000010960ed71 _TPA__TTRXFo_oGSqCSo7NSError__dT__XFo_iGSqS___iT__ + 81
    12  Doner                               0x000000010960c5e0 _TTRXFo_iGSqCSo7NSError__iT__XFo_oGSqS___dT__ + 32
    13  Doner                               0x000000010960c62c _TTRXFo_oGSqCSo7NSError__dT__XFdCb_dGSqS___dT__ + 60
    14  Doner                               0x0000000109682964 __69-[FIRAuthBackendRPCImplementation postWithRequest:response:callback:]_block_invoke + 944
    15  Doner                               0x0000000109765e78 __76-[GSDK_GTMSessionFetcher invokeFetchCallbacksOnCallbackQueueWithData:error:]_block_invoke + 25
    16  libdispatch.dylib                   0x000000010dcb8d9d _dispatch_call_block_and_release + 12
    17  libdispatch.dylib                   0x000000010dcd93eb _dispatch_client_callout + 8
    18  libdispatch.dylib                   0x000000010dcbf82c _dispatch_queue_drain + 2215
    19  libdispatch.dylib                   0x000000010dcbed4d _dispatch_queue_invoke + 601
    20  libdispatch.dylib                   0x000000010dcc1996 _dispatch_root_queue_drain + 1420
    21  libdispatch.dylib                   0x000000010dcc1405 _dispatch_worker_thread3 + 111
    22  libsystem_pthread.dylib             0x000000010e02d4de _pthread_wqthread + 1129
    23  libsystem_pthread.dylib             0x000000010e02b341 start_wqthread + 13
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

您的Firebase身份验证调用很可能在不是主线程的线程中返回。 我对执行网络事务的第三方库也遇到了类似的问题。 要解决此问题，请使用对主UI线程的调度来包装警报代码：

FIRAuth.auth()?.sendPasswordResetWithEmail(txtEmail.text!, completion: { (error) in
    dispatch_async(dispatch_get_main_queue()) {
        var title = ""
        var message = ""

        if error != nil {
            title = "Error"
            message = (error?.localizedDescription)!
        } else {
            title = "Success!"
            message = "Password reset email sent."
            self.txtEmail.text = ""
        }


        let alertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
        let defaultAction = UIAlertAction(title: "Ok", style: .Cancel, handler: nil)
        alertController.addAction(defaultAction)

        self.presentViewController(alertController, animated: true, completion: nil)
    }
})