Configured The Default Firebase App __FIRAPP_DEFAULT

Answer :

In my particular workflow, when adding firebase dependencies, the tutorial code and flutter warnings never prompted to modify the AppDelegate.m file. It wasn't until I dialed back and added cloud_firestore did I get prompted with this warning:

6.3.0 - [Firebase/Core][I-COR000003] The default Firebase app has not yet been configured. Add [FIRApp configure]; (FirebaseApp.configure() in Swift) to your application initialization.

Read more: [https://firebase.google.com/docs/ios/setup#initialize_firebase_in_your_app].

1. open xc workspace >> open ios/Runner.xcworkspace


2. open AppDelegate.m


3. in AppDelegate.m add the following line:

import Firebase;

4. in AppDelegate.m add the following snippet to your application did finish method

[FIRApp configure];

Here is what mine looked like in the end:

This worked for me:
https://medium.com/vector-com-mm/how-to-fix-ios-crash-during-the-start-firebase-configure-f3477df3154

In AppDelegate.swift change the order of

GeneratedPluginRegistrant.register(with: self)
FirebaseApp.configure()

to:

FirebaseApp.configure() 
GeneratedPluginRegistrant.register(with: self)

clean and rebuild...

My AppDelegate.swift

import UIKit
import Flutter
import Firebase

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    FirebaseApp.configure()
    GeneratedPluginRegistrant.register(with: self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}