Crash while trying to forward method from RxApplicationDelegateProxy

[zulkis]

I implemented UNUserNotificationCenterDelegate protocol in my AppDelegate,
then use UIApplication.shared.rx.appState.map...etc

Then after getting push from system RxApplicationDelegateProxy crashed with unrecognized selector at [RxAppState.RxApplicationDelegateProxy userNotificationCenter:didReceiveNotificationResponse:withCompletionHandler:]

After a bit of debugging it seems that forward delegate in RxCocoa's DelegateProxy is nil

[pixeldock]

Thanks for opening the issue. I'll try to reproduce the issue.

[zulkis]

This issues #6
should not be a case, since original call coming from iOS itself in that case.

Also, should not be a case in ObjectiveC, since we could cast UIApplication.sharedApplication.delegate to (id) and as a user of it - I should not worry how Proxy handles forwarding.

[zulkis]

Wow, interesting case.
My AppDelegate is ObjectiveC based.

Next screenshots I could not fully understand.
Stacktrace is the same.
1st one is when original setForwardingToDelegate called. We see our RawPointer to AppDelegate:

Next call is a RxCocoa call:

Delegate is nil.

[zulkis]

From the other side, ObjectiveC side of RxCocoa setter is working:

-(void)_setForwardToDelegate:(id __nullable)forwardToDelegate retainDelegate:(BOOL)retainDelegate {
    __forwardToDelegate = forwardToDelegate;
    if (retainDelegate) {
        self.strongForwardDelegate = forwardToDelegate; // self.strongForwardDelegate is existing
    }
    else {
        self.strongForwardDelegate = nil;
    }
}

So my screenshots could be easily misleading since xcode bug of showing bridgeable variables to be nil

[zulkis]

Implementing

override open func forwardingTarget(for aSelector: Selector!) -> Any? {
            return self.forwardToDelegate()
}

Fixes an issue, but I am not sure if this solution stable should be done here or like issue in RxCocoa
@pixeldock

[pixeldock]

I did not have time to setup a new Objective-C project yet but I tried your scenario with one of my Swift projects. Everything is working fine when your AppDelegate is a Swift class. The issue seems to be related to having a Objective-C AppDelegate.

I think we should open a new issue at RxCocoa.

[pixeldock]

@zulkis Thanks!

[kanstraktar]

Any update on this? I'm having the same issue in a mixed Objective C/Swift project, AppDelegate being ObjC. Thanks

[pixeldock]

@kanstraktar Unfortunately this issue seems to be caused by something inside RxSwift. There is an open PR (ReactiveX/RxSwift#1503) with a fix but there seems to be some uncertainty why the fix is needed . Have you tried the suggested fix? Maybe you can provide some additional info there?

[pixeldock]

I'll close this issue as this has not seen any feedback for over a year. Thank you guys for your feedback!

[Tayphoon]

It was easy recreate this crash if you have objective-c app with code like this in app delegate

@implementation AppDelegate

+ (instancetype)sharedDelegate {
    return (AppDelegate*)[UIApplication sharedApplication].delegate;
}

Now any calls sharedDelegate in objective-c will return proxy and crash when you try access to any property of AppDelegate.

2019-08-17 21:20:08.183948+0300 CS DEV[3789:29536] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[RxAppState.RxApplicationDelegateProxy managedObjectContext]: unrecognized selector sent to instance 0x600003ed3240'