Message sent to a deallocated instance

Question

Background: All my OpenTok methods are in one `ViewController` that gets pushed into view, like a typical Master/detail VC relationship. The detailVC connects you to a different room depending on your selection. When I press the back button to pop the view away, I get a crash (maybe 1 out of 7 times): ``` [OTMessenger setRumorPingForeground] message sent to deallocated instance xxxxx ``` or ``` [OTSession setSessionConnectionStatus:]: message sent to deallocated instance 0x1e1ee440 ``` I put my unpublish/disconnect methods in viewDidDisappear: ``` -(void)viewDidDisappear:(BOOL)animated{ //dispatch_async(self.opentokQueue, ^{ [self.session removeObserver:self forKeyPath:@"connectionCount"]; if(self.subscriber){ [self.subscriber close]; self.subscriber = nil; } if (self.publisher) { [self doUnpublish]; } if (self.session) { [self.session disconnect]; self.session = nil; } //}); [self doCloseRoomId:self.room.roomId position:self.room.position]; } ``` Here is a trace: Here is the DetailVi…

Accepted Answer

Closing the session from `viewWillDisappear()` works if you can determine for sure that the view is going to be popped, not pushed or hidden. Some answers suggest putting this code in `dealloc()`. Regarding those suggestions, Apple says,

You should try to avoid managing the lifetime of limited resources using dealloc.

So, here is how you can determine for sure that your view will get popped. `viewWillDisappear()` is called when the view is popped from the stack, or is otherwise pushed somewhere else. This is the easiest way to determine which, and then unpublish/disconnect if it is truly popped. You can test for this with `isMovingFromParentViewController`. Also, here is where you can remove specific observers.

```
- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated]

// This is true if the view controller is popped
    if ([self isMovingFromParentViewController])
    {
        NSLog(@"View controller was popped");

// Remove observer
        [[NSNotificationCenter defaultCenter] removeObserver:self.session];

...

//dispatch_async(self.opentokQueue, ^{
            if(self.subscriber){
                [self.subscriber close];
                self.subscriber = nil;
            }

if (self.publisher) {
                [self doUnpublish];
            }

if (self.session) {
                [self.session disconnect];
                self.session = nil;
            }
            //});
            [self doCloseRoomId:self.room.roomId position:self.room.position];
    }
    else
    {
        NSLog(@"New view controller was pushed");
    }
}
```

Ref: Testing for Specific Kinds of View Transitions

Message sent to a deallocated instance

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