ios - 使用 Firebase Auth 时应用崩溃，原因 : 'Default app has already been configured.'

Question

我正在构建我的第一个 iOS 应用程序，我正在使用 Firebase 处理身份验证、数据库等。我添加了一个注册屏幕并使用以下代码创建了一个新用户:

FIRAuth.auth()?.createUserWithEmail(emailAddress.text!, password: password.text!, completion: { (user, error) in

        })

当用户点击注册按钮时，会有一个 segue 将他们带回原始登录 View Controller 。但是，当我开始运行该应用程序时，它卡在启动屏幕上。这是调试器输出:

2016-06-19 14:35:05.402 unitaskr[4386:82981] Configuring the default app.
2016-06-19 14:35:05.413 unitaskr[4386:] <FIRAnalytics/INFO> Firebase Analytics     v.3200000 started
2016-06-19 14:35:05.414 unitaskr[4386:] <FIRAnalytics/INFO> To enable debug logging set the following application argument: -FIRAnalyticsDebugEnabled (see ...)
2016-06-19 14:35:05.419: <FIRInstanceID/WARNING> FIRInstanceID AppDelegate proxy enabled, will swizzle app delegate remote notification handlers. To disable add "FirebaseAppDelegateProxyEnabled" to your Info.plist and set it to NO
2016-06-19 14:35:05.418 unitaskr[4386:] <FIRAnalytics/INFO> Successfully created Firebase Analytics App Delegate Proxy automatically. To disable the proxy, set the flag FirebaseAppDelegateProxyEnabled to NO in the Info.plist
2016-06-19 14:35:05.430 unitaskr[4386:82981] *** Terminating app due to uncaught exception 'com.firebase.core', reason: 'Default app has already been configured.'
*** First throw call stack:
(
0   CoreFoundation                      0x00000001100a8d85   __exceptionPreprocess + 165
1   libobjc.A.dylib                     0x00000001108e7deb objc_exception_throw + 48
2   CoreFoundation                      0x00000001100a8cbd +[NSException raise:format:] + 205
3   unitaskr                            0x000000010b58844d +[FIRApp    configureDefaultAppWithOptions:sendingNotifications:] + 102
4   unitaskr                            0x000000010b588238 +[FIRApp configure] + 302
5   unitaskr                            0x000000010b541f1a _TFC8unitaskr11AppDelegate11applicationfTCSo13UIApplication29didFinishLaunchingWithOptionsGSqGVs10DictionaryCSo8NSObjectPs9AnyObject____Sb + 266
6   unitaskr                            0x000000010b542204 _TToFC8unitaskr11AppDelegate11applicationfTCSo13UIApplication29didFinishLaunchingWithOptionsGSqGVs10DictionaryCSo8NSObjectPs9AnyObject____Sb + 180
7   UIKit                               0x000000010e5bf9ac -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 272
8   UIKit                               0x000000010e5c0c0d -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 3415
9   UIKit                               0x000000010e5c7568 -[UIApplication _runWithMainScene:transitionContext:completion:] + 1769
10  UIKit                               0x000000010e5c4714 -[UIApplication workspaceDidEndTransaction:] + 188
11  FrontBoardServices                  0x00000001127b78c8 __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 24
12  FrontBoardServices                  0x00000001127b7741 -[FBSSerialQueue _performNext] + 178
13  FrontBoardServices                  0x00000001127b7aca -[FBSSerialQueue _performNextFromRunLoopSource] + 45
14  CoreFoundation                      0x000000010ffce301 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
15  CoreFoundation                      0x000000010ffc422c __CFRunLoopDoSources0 + 556
16  CoreFoundation                      0x000000010ffc36e3 __CFRunLoopRun + 867
17  CoreFoundation                      0x000000010ffc30f8 CFRunLoopRunSpecific + 488
18  UIKit                               0x000000010e5c3f21 -[UIApplication _run] + 402
19  UIKit                               0x000000010e5c8f09 UIApplicationMain + 171
20  unitaskr                            0x000000010b542a42 main + 114
21  libdyld.dylib                       0x00000001113b692d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

我可以根据需要提供其他信息，任何帮助/建议都将不胜感激，因为我刚刚起步并希望尽可能多地学习。祝你有美好的一天!

Answer 1

我在使用消息扩展 时遇到了问题:

如果您在App Extension 中，您没有委托(delegate)，您必须将 FIRApp.configure() 放在主 ViewController 的初始化中(或在 viewDidLoad 中作为建议)。

问题是:在消息扩展中，如果用户在打开您的扩展的线程中按下多条消息，init(或 viewdidLoad)将被调用多次，因此由于多次调用 FIRApp.configure() 而崩溃...

我找到的解决方案是在主视图 Controller 中创建一个静态 bool 值:

    static var isAlreadyLaunchedOnce = false // Used to avoid 2 FIRApp configure

我在 init 或 viewDidLoad 中调用 FIRApp.configure() 之前对其进行了测试:

// Configure Firebase
    // ------------------
    // We check if FIRApp has already been configured with a static var, else it will crash...
    if !MessagesViewController.isAlreadyLaunchedOnce {
        FIRApp.configure()

        MessagesViewController.isAlreadyLaunchedOnce = true
    }

这样，就不会再发生崩溃了。

---

哦，我在这里找到了一个更优雅的方法来解决这个问题: iOS Extension - Fatal Exception: com.firebase.core Default app has already been configured

    // Configure Firebase
    // ------------------
    if FIRApp.defaultApp() == nil {
        FIRApp.configure()            
    }

这样就不再是静态的 ;)