Error: `call FirebaseApp.configure() before using Firestore`

问题

Background Info

I have started developing a backend for an simple App, and I have set up a database class (named DBDelegate) that all the files will communicate with. In my AppDelegate.swift I have this:

static public var dbDelegate:DBDelegate = DBDelegate()

private func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.
    FirebaseApp.configure()
    return true
}

Its a static public so I can access the dbDelegate from other files.

In my other files, I have the following to help readability: (because it is a class it will pass by reference)

let dbDelegate = AppDelegate.dbDelegate

In my DBDelegate class:

var db = Firestore.firestore()
init() {
    FirebaseApp.configure()
}

Building and Running

When I build my code, it builds fine.

On run, the app promptly crashes with SIGABRT. The error message is:
Terminating app due to uncaught exception 'FIRAppNotConfiguredException', reason: 'Failed to get FirebaseApp instance. Please call FirebaseApp.configure() before using Firestore'

What I have tried

• I have tried putting a breakpoint on the init function in the DBDelegate class. It does not reach the breakpoint.
• I have tried making the all the dbDelegate variables lazy:
  • I got a compile error for the one in AppDelegate: lazy must not be used on an already-lazy global
  • Runtime errors for others: please call FirebaseApp.configure() before using Firestore.
• I have tried the following (assigning dbDelegate in didFinishLaunchingWithOptions):

    static public var dbDelegate:DBDelegate!
    private func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        FirebaseApp.configure()
        dbDelegate = DBDelegate()
        return true
    }

• I get Compile error: Static member 'dbDelegate' cannot be used on instance of type 'AppDelegate'

Any help would be great!

Edit: I found a janky solution, see below.

回答1:

It would be better to create a new singleton for Firebase.

class FirebaseService: NSObject {
    static let shared = FirebaseService()

    init() {
         FirebaseApp.configure()
    }
}

Then you can access everything via shared like:

FirebaseService.shared.methodName

For configuring in app delegate you would need to call it like:

_ = FirebaseService.shared

回答2:

Firstly, I would like to thank @DionzB for suggesting using singletons (which I did). I will reference his/her post in this answer.

Ok, so after some research and playing with breakpoints, I found that my custom class actually executes before the AppDelegate. Knowing such, I created a variable before the following line:

static let shared = FirebaseService()

the name does not matter, because I/you will not call it, and assign it to FirebaseApp.configure()

The FirebaseService class becomes:

class FirebaseService: NSObject {
    let constantToNeverTouch = FirebaseApp.configure()
    static let shared = FirebaseService()

    init() {
    }
}

Next, you must make sure that FirebaseApp.configure() is no where else in your code. It should not be in the AppDelegate either. Having multiple FirebaseApp.configure()'s crashes the app.

回答3:

You can override the AppDelegate init method with FirebaseApp.configure() and make sure it loads before any windows are created.

override init() {
        FirebaseApp.configure()
}

回答4:

Chances are your code are in the wrong order. Make sure your window code are put AFTER the firebaseApp.configure and not before. I was getting the same crash until I simply placed my window creation codes: (window = UIWindow(frame: UIScreen.main.bounds), etc) after the firebaseApp.configure connection .Just swapped their placement:

    FirebaseApp.configure()
    let db = Firestore.firestore()
    let settings =  db.settings
    settings.areTimestampsInSnapshotsEnabled = true
    db.settings = settings

    window = UIWindow(frame: UIScreen.main.bounds)
    window?.rootViewController = HomeController()
    window?.makeKeyAndVisible()

回答5:

let dbDelegate = AppDelegate.dbDelegate

In your DBDelegate class:

var db : Firestore?
init() {
    FirebaseApp.configure()
    db = Firestore.firestore()
}

来源：https://stackoverflow.com/questions/53469351/error-call-firebaseapp-configure-before-using-firestore