Fatal Exception: NSInvalidArgumentException while working with UISwitch in UITableview - ios

Question

AppName denotes the application name.
User reported this crash. It only came once and also not able to reproduce the same on my end. Hence not able to debug. If some one can provide some insight for the same.
Below is the Crashlytics log received.
# OS Version: 12.4.2 (16G114)
# Device: iPhone 5s
# RAM Free: 8.5%
# Disk Free: 9.6%
#0. Crashed: com.twitter.crashlytics.ios.exception
0 App Name 0x100df7388 CLSProcessRecordAllThreads + 376 (CLSProcess.c:376)
1 App Name 0x100df7770 CLSProcessRecordAllThreads + 407 (CLSProcess.c:407)
2 App Name 0x100de7474 CLSHandler + 26 (CLSHandler.m:26)
3 App Name 0x100df599c __CLSExceptionRecord_block_invoke + 198 (CLSException.mm:198)
4 libdispatch.dylib 0x1db6217d4 _dispatch_client_callout + 16
5 libdispatch.dylib 0x1db5cfc1c _dispatch_lane_barrier_sync_invoke_and_complete + 56
6 App Name 0x100df5444 CLSExceptionRecord + 205 (CLSException.mm:205)
7 App Name 0x100df5278 CLSExceptionRecordNSException + 102 (CLSException.mm:102)
8 App Name 0x100df4e9c CLSTerminateHandler() + 258 (CLSException.mm:258)
9 libc++abi.dylib 0x1dadb0838 std::__terminate(void (*)()) + 16
10 libc++abi.dylib 0x1dadb0434 __cxa_rethrow + 144
11 libobjc.A.dylib 0x1dadbbbc8 objc_exception_rethrow + 44
12 CoreFoundation 0x1dbb72030 CFRunLoopRunSpecific + 544
13 GraphicsServices 0x1ddd7379c GSEventRunModal + 104
14 UIKitCore 0x2084f3c38 UIApplicationMain + 212
15 App Name 0x100c1ee1c main + 23 (ViewController.swift:23)
16 libdyld.dylib 0x1db6328e0 start + 4
--
Fatal Exception: NSInvalidArgumentException
0 CoreFoundation 0x1dbbe6190 __exceptionPreprocess
1 libobjc.A.dylib 0x1dadbb9f8 objc_exception_throw
2 CoreFoundation 0x1dbaf03b0 -[NSCache init]
3 CFNetwork 0x1dc3f4b58 -[NSURLSessionTask cancel]
4 App Name 0x100cb9fec ViewController.switchChanged(_:) (ViewController.swift)
5 App Name 0x100cbac7c #objc ViewController.switchChanged(_:) (<compiler-generated>)
6 UIKitCore 0x2084f5300 -[UIApplication sendAction:to:from:forEvent:]
7 UIKitCore 0x207f9e424 -[UIControl sendAction:to:forEvent:]
8 UIKitCore 0x207f9e744 -[UIControl _sendActionsForEvents:withEvent:]
9 UIKitCore 0x207fcb0fc -[UISwitchModernVisualElement sendStateChangeActions]
10 UIKitCore 0x207fcaa04 -[UISwitchMVEGestureTrackingSession _sendStateChangeActionsIfNecessary]
11 UIKitCore 0x207fcb7a4 -[UISwitchModernVisualElement _handleLongPressWithGestureLocationInBounds:gestureState:]
12 UIKitCore 0x20811cac4 -[UIGestureRecognizerTarget _sendActionWithGestureRecognizer:]
13 UIKitCore 0x208124ccc _UIGestureRecognizerSendTargetActions
14 UIKitCore 0x208122670 _UIGestureRecognizerSendActions
15 UIKitCore 0x208121b9c -[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:]
16 UIKitCore 0x208115c78 _UIGestureEnvironmentUpdate
17 UIKitCore 0x2081153a8 -[UIGestureEnvironment _deliverEvent:toGestureRecognizers:usingBlock:]
18 UIKitCore 0x208115188 -[UIGestureEnvironment _updateForEvent:window:]
19 UIKitCore 0x20852d7d0 -[UIWindow sendEvent:]
20 UIKitCore 0x20850d85c -[UIApplication sendEvent:]
21 UIKitCore 0x2085d39d4 __dispatchPreprocessedEventFromEventQueue
22 UIKitCore 0x2085d6100 __handleEventQueueInternal
23 UIKitCore 0x2085cf330 __handleHIDEventFetcherDrain
24 CoreFoundation 0x1dbb77f2c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__
25 CoreFoundation 0x1dbb77eac __CFRunLoopDoSource0
26 CoreFoundation 0x1dbb77794 __CFRunLoopDoSources0
27 CoreFoundation 0x1dbb726d0 __CFRunLoopRun
28 CoreFoundation 0x1dbb71fc4 CFRunLoopRunSpecific
29 GraphicsServices 0x1ddd7379c GSEventRunModal
30 UIKitCore 0x2084f3c38 UIApplicationMain
31 App Name 0x100c1ee1c main + 23 (ViewController.swift:23)
32 libdyld.dylib 0x1db6328e0 start
Below is some part of code which may give more clear picture.
case .SettingsCell:
let cell: SettingsCell = tableView.dequeueReusableCell(withIdentifier: "SettingsCell") as! SettingsCell
cell.selectionStyle = .none
cell.switchOnOff.addTarget(self, action: #selector(switchChanged(_ :)), for: .valueChanged)
Below is the function called on UISwitch button value change.
case 13:
if sender.isOn{
UserDefaultUtility.saveToUserDefault(value: true, key: Constant.UserDefaults.k_IsAnimation)
appDelegate.getPollutantAbbreviationAndGIFImages()
} else {
let networkManager = NetworkManager()
networkManager.cancelImageDownloadTask()
}
Below is the function in Network Manager:
func cancelImageDownloadTask() {
self.downloadImagesSession?.cancel()
}
Download session is URLSessionDownloadTask object declared below.
weak var downloadImagesSession: URLSessionDownloadTask?
It is allocated using below code.
self.downloadImagesSession = session.downloadTask(with: request) { (tempLocalUrl, response, error) in
}

Answer 1

That seems to be the problem:
let networkManager = NetworkManager()
networkManager.cancelImageDownloadTask()
You just initialize a NetworkManager instance, and then directly try to cancel a task. But you cannot cancel a task which isn't started yet