App crashing when App is setting delegate of FirebaseMessaging - ios

Question

My app try to use Firebase remote notification, I followed the Firebase guide. Now my app crashes in AppDelegate where I am trying to set the delegate of Firebase messaging.
Here is the code
[FIRApp configure];
[FIRMessaging messaging].delegate = self;
In the second line it crashes with crash message as given below:
+[FIRInstanceIDCheckinPreferences preferencesFromKeychainContents:]: unrecognized selector sent to class 0x10ef2a538
* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason:
'+[FIRInstanceIDCheckinPreferences preferencesFromKeychainContents:]:
unrecognized selector sent to class 0x10ef2a538'
* First throw call stack: ( 0 CoreFoundation 0x00000001116671e6 exceptionPreprocess + 294 1 libobjc.A.dylib
0x0000000110cfc031 objc_exception_throw + 48 2 CoreFoundation
0x00000001116e86c4 +[NSObject(NSObject) doesNotRecognizeSelector:] +
132 3 CoreFoundation 0x00000001115e9898
___forwarding_ + 1432 4 CoreFoundation 0x00000001115e9278 _CF_forwarding_prep_0 + 120 5 MobilePro Dev
0x000000010ed09af3 -[FIRInstanceIDCheckinStore
cachedCheckinPreferences] + 407 6 MobilePro Dev
0x000000010ed0d73a -[FIRInstanceIDStore resetCredentialsIfNeeded] +
145 7 MobilePro Dev 0x000000010ed0d230
-[FIRInstanceIDStore initWithCheckinStore:tokenStore:delegate:] + 174 8 MobilePro Dev 0x000000010ed0d154
-[FIRInstanceIDStore initWithDelegate:] + 142 9 MobilePro Dev 0x000000010ed10acc -[FIRInstanceIDTokenManager init] + 105 10
MobilePro Dev 0x000000010ed022ae -[FIRInstanceID
setupTokenManager] + 50 11 MobilePro Dev
0x000000010ed0225c -[FIRInstanceID start] + 90 12 libdispatch.dylib
0x0000000114c4f7ec _dispatch_client_callout + 8 13 libdispatch.dylib
0x0000000114c50d64 dispatch_once_f + 285 14 MobilePro Dev
0x000000010ecfefac +[FIRInstanceID instanceID] + 45 15 MobilePro Dev
0x000000010ed26a6a -[FIRMessaging initPrivately] + 38 16 MobilePro
Dev 0x000000010ed26939 25+[FIRMessaging
messaging]_block_invoke + 41 17 libdispatch.dylib
0x0000000114c4f7ec _dispatch_client_callout + 8 18 libdispatch.dylib
0x0000000114c50d64 dispatch_once_f + 285 19 MobilePro Dev
0x000000010ed2690d +[FIRMessaging messaging] + 45 20 MobilePro Dev
0x000000010eaa9ac3 -[AppDelegate
application:didFinishLaunchingWithOptions:] + 323 21 UIKit
0x00000001128d96fb -[UIApplication
_handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 278 22 UIKit 0x00000001128db172
-[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 4123 23 UIKit 0x00000001128e05cb
-[UIApplication _runWithMainScene:transitionContext:completion:] + 1677 24 UIKit 0x0000000112ca2f7e
__111-[__UICanvasLifecycleMonitor_Compatability _scheduleFirstCommitForScene:transition:firstActivation:completion:]_block_invoke
+ 866 25 UIKit 0x0000000113075a39 +[_UICanvas _enqueuePostSettingUpdateTransactionBlock:] + 153 26 UIKit 0x0000000112ca2bba
-[__UICanvasLifecycleMonitor_Compatability _scheduleFirstCommitForScene:transition:firstActivation:completion:] + 236 27 UIKit 0x0000000112ca33db
-[__UICanvasLifecycleMonitor_Compatability activateEventsOnly:withContext:completion:] + 675 28 UIKit
0x0000000113614614 __82-[_UIApplicationCanvas
_transitionLifecycleStateWithTransitionContext:completion:]_block_invoke
+ 299 29 UIKit 0x00000001136144ae -[_UIApplicationCanvas _transitionLifecycleStateWithTransitionContext:completion:] + 433 30 UIKit 0x00000001132f875d
__125-[_UICanvasLifecycleSettingsDiffAction performActionsForCanvas:withUpdatedScene:settingsDiff:fromSettings:transitionContext:]_block_invoke
+ 221 31 UIKit 0x00000001134f34b7 _performActionsWithDelayForTransitionContext + 100 32 UIKit 0x00000001132f8627 -[_UICanvasLifecycleSettingsDiffAction
performActionsForCanvas:withUpdatedScene:settingsDiff:fromSettings:transitionContext:]
+ 223 33 UIKit 0x00000001130750e0 -[_UICanvas scene:didUpdateWithDiff:transitionContext:completion:] + 392 34 UIKit 0x00000001128deeac
-[UIApplication workspace:didCreateScene:withTransitionContext:completion:] + 515 35
UIKit 0x0000000112eb1bcb
-[UIApplicationSceneClientAgent scene:didInitializeWithEvent:completion:] + 361 36
FrontBoardServices 0x00000001176452f3 -[FBSSceneImpl
_didCreateWithTransitionContext:completion:] + 331 37 FrontBoardServices 0x000000011764dcfa
__56-[FBSWorkspace client:handleCreateScene:withCompletion:]_block_invoke_2 + 225 38
libdispatch.dylib 0x0000000114c4f7ec
_dispatch_client_callout + 8 39 libdispatch.dylib 0x0000000114c54db8 _dispatch_block_invoke_direct + 592 40
FrontBoardServices 0x0000000117679470
__FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK + 24 41 FrontBoardServices 0x000000011767912e
-[FBSSerialQueue _performNext] + 439 42 FrontBoardServices 0x000000011767968e -[FBSSerialQueue _performNextFromRunLoopSource] +
45 43 CoreFoundation 0x0000000111609bb1
CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION + 17 44 CoreFoundation 0x00000001115ee4af
__CFRunLoopDoSources0 + 271 45 CoreFoundation 0x00000001115eda6f __CFRunLoopRun + 1263 46 CoreFoundation
0x00000001115ed30b CFRunLoopRunSpecific + 635 47 GraphicsServices
0x000000011779ca73 GSEventRunModal + 62 48 UIKit
0x00000001128e2057 UIApplicationMain + 159 49 MobilePro Dev
0x000000010eac56cf main + 111 50 libdyld.dylib
0x0000000114ccc955 start + 1 51 ???
0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with
uncaught exception of type NSException

Answer 1

If you don't use pods, you must to add the objC linker flag for your target.
From the documentation:
"Integrate without CocoaPods
If you don't want to use Cocoapods, you can still take advantage of the Firebase SDKs by importing the frameworks directly.
Download the framework SDK zip. This is a ~1GB file and might take some time to download.
Unzip the file, then review the README for the Frameworks that you want to include in your app.
Add the ObjC linker flag in your Other Linker Settings in your target's build settings."
Link:
https://firebase.google.com/docs/ios/setup
https://developer.apple.com/library/archive/qa/qa1490/_index.html

Answer 2

When you call a delegate, you must ensure that all the required methods of that delegate are written.
Check the following method is called in your Appdelegate.
-(void)messaging:(FIRMessaging *)messaging didReceiveRegistrationToken:(NSString *)fcmToken
{
}
Or ensure that FIRMessagingDelegate is written in your Appdelegate
#interface AppDelegate ()<FIRMessagingDelegate>

Answer 3

You need to change the Firebase configure method.
Call it as,
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 42.0), dispatch_get_main_queue(), ^{
[FIRApp configure];
});
It will solve your issue.

Answer 4

import FirebaseMessaging
FirebaseApp.configure()
Messaging.messaging().delegate = self
//MARK:- Messaging Delegate Method ..............................
func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
let token = Messaging.messaging().fcmToken
print("FCM token: \(token ?? "")")
}