"currentDevice.torchAvailable" crash

[Stuart Tett]

Fatal Exception: NSInternalInconsistencyException
Cannot update for observer <PBJVision 0x15c75cfb0> for the key path "currentDevice.torchAvailable" from <PBJVision 0x15c75cfb0>, most likely because the value for the key "currentDevice" has changed without an appropriate KVO notification being sent. Check the KVO-compliance of the PBJVision class.

Fatal Exception: NSInternalInconsistencyException
0  CoreFoundation                 0x182da6e38 __exceptionPreprocess
1  libobjc.A.dylib                0x18240bf80 objc_exception_throw
2  CoreFoundation                 0x182da6d80 -[NSException initWithCoder:]
3  Foundation                     0x1836c79f8 -[NSKeyValueNestedProperty object:withObservance:didChangeValueForKeyOrKeys:recurse:forwardingValues:]
4  Foundation                     0x1836a3a24 NSKeyValueDidChange
5  Foundation                     0x18368e6b4 -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:]
6  PBJVision                      0x1011e3160 __29-[PBJVision _sessionStarted:]_block_invoke (PBJVision.m:2351)

This seems to be our apps most common crashes in the app store recorded by crashlytics. Though I've not seen it happen on my personal device

[Stuart Tett]

The only place I can find where _currentDevice is being changed without will/DidChangeValueForKey is in _destroyCamera. So I'm guessing this could be it. I'm using setCurrentDevice in other places but this should automatically call it. And anywhere else I see the ivar changing, the will/Did are there.

Going to try changing it to this:

[self willChangeValueForKey:@"currentDevice"];
_currentDevice = nil;
[self didChangeValueForKey:@"currentDevice"];