Crash viewDidMoveToWindow:shouldAppearOrDisappear: on iOS 10 - ios

Question

Since a while my app crashes in production but It has been impossible to reproduce this error in debug mode.
The error in Crashlytics is:
UIKit
-[UIViewController viewDidMoveToWindow:shouldAppearOrDisappear:]
SIGABRT ABORT 0x00000001825d4d74
Crashed: com.apple.main-thread
0 libsystem_kernel.dylib 0x1825d4d74 __abort_with_payload + 8
1 libsystem_kernel.dylib 0x1825d1480 abort_with_payload_wrapper_internal + 100
2 libsystem_kernel.dylib 0x1825d141c abort_with_payload_wrapper_internal + 34
3 libobjc.A.dylib 0x18203fed8 _objc_fatalv(unsigned long long, unsigned long long, char const*, char*) + 112
4 libobjc.A.dylib 0x18203fe30 __objc_error + 42
5 libobjc.A.dylib 0x182052cd4 weak_entry_insert(weak_table_t*, weak_entry_t*) + 318
6 libobjc.A.dylib 0x182058664 objc_initWeak + 324
7 UIKit 0x1894ce1bc -[UIViewController viewDidMoveToWindow:shouldAppearOrDisappear:] + 2068
8 UIKit 0x18944db5c -[UIView(Internal) _didMoveFromWindow:toWindow:] + 1352
9 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
10 UIKit 0x189471714 -[UIScrollView _didMoveFromWindow:toWindow:] + 92
11 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
12 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
13 UIKit 0x189471714 -[UIScrollView _didMoveFromWindow:toWindow:] + 92
14 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
15 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
16 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
17 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
18 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
19 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
20 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
21 UIKit 0x18944d8e4 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 720
22 UIKit 0x18944cd90 __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 156
23 Foundation 0x184034510 -[NSISEngine withBehaviors:performModifications:] + 168
24 UIKit 0x18944cc04 -[UIView(Hierarchy) _postMovedFromSuperview:] + 820
25 UIKit 0x18974a078 __UIViewWasRemovedFromSuperview + 172
26 UIKit 0x18944bc80 -[UIView(Hierarchy) removeFromSuperview] + 512
27 UIKit 0x1897a23dc __71-[UIPresentationController _initViewHierarchyForPresentationSuperview:]_block_invoke.629 + 1044
28 UIKit 0x18979c4fc -[UIPresentationController transitionDidFinish:] + 124
29 UIKit 0x18990afc8 -[_UICurrentContextPresentationController transitionDidFinish:] + 40
30 UIKit 0x1897a012c __56-[UIPresentationController runTransitionForCurrentState]_block_invoke_2 + 188
31 UIKit 0x189578ad4 -[_UIViewControllerTransitionContext completeTransition:] + 116
32 UIKit 0x1895788c0 -[UITransitionView notifyDidCompleteTransition:] + 252
33 UIKit 0x1895783dc -[UITransitionView _didCompleteTransition:] + 1240
34 UIKit 0x189577ef0 -[UITransitionView _transitionDidStop:finished:] + 124
35 UIKit 0x189489b48 -[UIViewAnimationState sendDelegateAnimationDidStop:finished:] + 312
36 UIKit 0x189489988 -[UIViewAnimationState animationDidStop:finished:] + 160
37 QuartzCore 0x186912404 CA::Layer::run_animation_callbacks(void*) + 260
38 libdispatch.dylib 0x1824911c0 _dispatch_client_callout + 16
39 libdispatch.dylib 0x182495d6c _dispatch_main_queue_callback_4CF + 1000
40 CoreFoundation 0x1835b5f2c __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
41 CoreFoundation 0x1835b3b18 __CFRunLoopRun + 1660
42 CoreFoundation 0x1834e2048 CFRunLoopRunSpecific + 444
43 GraphicsServices 0x184f65198 GSEventRunModal + 180
44 UIKit 0x1894bc628 -[UIApplication _run] + 684
45 UIKit 0x1894b7360 UIApplicationMain + 208
46 <App Name> 0x100081590 main (main.m:14)
47 libdispatch.dylib 0x1824c45b8 (Missing)
Most of the logs show that the user had between 1% and 3% of RAM memory free but there are some with more than 10%.
Also my app tracks errors using Sentry but this error is not in Sentry only in Fabric.
Most of my users use iOS 10 but still there are who use iOS 9 and this crash seems that not affect these users. So it seems it is related to iOS 10.
Also I have searched here but I have not could find a solution even a clue. Someone could help me to find a clue?
EDIT
Regarding the comments the new code introduced that it is related with UIViewController is:
- (IBAction)tapClose:(id)sender {
[self close];
}
- (void)close {
_dismissing = YES;
CGFloat height = self.view.superview.frame.size.height;
[UIView animateWithDuration:0.2 animations:^{
[self.view setFrame:CGRectMake(0, height, self.view.frame.size.width, self.view.frame.size.height)];
_overlay.alpha = 0;
} completion:^(BOOL finished) {
if (finished) {
[self.view removeFromSuperview];
[_overlay removeFromSuperview];
if (self.blockWhenClose) {
self.blockWhenClose();
}
}
}];
}
- (void)showIn:(UIViewController *)viewcontroller {
CGRect frame = viewcontroller.view.frame;
CGFloat height = [self calculateHeight:frame.size.height / 2];
[self.view setFrame:CGRectMake(0, frame.size.height, frame.size.width, height)];
[_overlay setFrame:frame];
_overlay.alpha = 0;
[viewcontroller addChildViewController:self];
[viewcontroller.view addSubview:_overlay];
[viewcontroller.view addSubview:self.view];
[self didMoveToParentViewController:viewcontroller];
[UIView animateWithDuration:_duration animations:^{
_overlay.alpha = 1;
[self.view setFrame:CGRectMake(0, frame.size.height - height, frame.size.width, height)];
}];
_show = YES;
}
But I do not know where exactly the crash occurs.

Answer 1

For me this started with iOS 14
The problem was, I had code where the view of a controller (A) was added as a subview to another controller(B) without holding a reference to the controller(A) itself. the controller(A) was deallocated and next time the view is about to appear or disappear, it tries to notify the controller(A) which causes a crashes.
Solution:
Manually hold a reference to the controller
OR addChildViewController which does the above for you