Memory leak when displaying a modal view and dismissing it - swift

Question

When an AVExportSession is finished exporting, I have my app display a modal view displaying the video and an array of images. Dismissing the modal view, and making it display again over and over shows a memory increase that continuously grows. I'm suspicious of a strong reference cycle that could be occurring.
I'm setting required variables on the modal view (manageCaptureVC). fileURL is a global variable that manageCaptureVC can read from to get the video. The video is removed based on that URL when the modal view is dismissed. The leak is larger depending on the size of the media that is captured and displayed in the modal view.
I have used the Leaks Instrument. Unfortunately, it never points to any of my functions. It shows memory addresses that displays assembly language. I am also using a device.
Here is a screen shot of my leaks instrument at the point I display and dismiss my view, and the instrument indicates leaks:
Anything obvious what could cause a leak in my case?
Presenting the modal view (manageCaptureVC)
// video done exporting
guard let exporter = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality) else { return }
exporter.outputURL = mainVideoURL
exporter.outputFileType = AVFileType.mov
let manageCaptureVC = self.storyboard?.instantiateViewController(withIdentifier: "ManageCaptureVC") as! ManageCaptureVC
exporter.exportAsynchronously(completionHandler: {[weak self]
() -> Void in
let fileManagement = FileManagement()
fileManagement.checkForAndDeleteExportFile() // delete export file
self?.myTimer.invalidate()
fileURL = mainVideoURL
guard let imgCaptureModeRawVal = self?.imageCaptureMode.rawValue else { return }
manageCaptureVC.imageCaptureMode = ManageCaptureVC.imageCaptureModes(rawValue: imgCaptureModeRawVal)!
manageCaptureVC.delegate = self
DispatchQueue.main.async(){
manageCaptureVC.modalPresentationStyle = .fullScreen
self?.present(manageCaptureVC, animated: true, completion: nil)
}
})
Dismissing the view:
func goBackTask(){
// turn off manage capture tutorial if needed
if debug_ManageCaptureTutorialModeOn {
debug_ManageCaptureTutorialModeOn = false
delegate?.resetFiltersToPrime()
}
// no longer ignore interface orientation
ignoreSelectedInterfaceOrientation = false
// remove observer for the application becoming active in this view
NotificationCenter.default.removeObserver(self,
name: UIApplication.didBecomeActiveNotification,
object: nil)
if let videoEndedObs = self.videoEndedObserver {
NotificationCenter.default.removeObserver(videoEndedObs)
}
// invalidate thumb timer
thumbColorTimer.invalidate()
// empty UIImages
uiImages.removeAll()
// delete video
let fileManagement = FileManagement()
fileManagement.checkForAndDeleteFile()
let group = DispatchGroup()
group.enter()
DispatchQueue.main.async {
self.enableButtons(enabled:false)
if let p = self.player, let pl = self.playerLayer {
p.pause()
pl.removeObserver(self, forKeyPath: "videoRect")
pl.removeFromSuperlayer()
p.replaceCurrentItem(with: nil)
}
group.leave()
}
let group2 = DispatchGroup()
group.notify(queue: .main) {
group2.enter()
DispatchQueue.main.async {
self.enableButtons(enabled:true)
group2.leave()
}
}
group2.notify(queue: .main) {
self.dismiss(animated: true)
}
}

Answer 1

I came across this problem as well. It took me days to track it down.
Setting modalPresentationStyle to .fullScreen resulted in the View Controller not being released. I was able to reproduce this on a trivially simple example.
I got round it by setting modalPresentationStyle to .currentContext.
None of the Instruments identified this retain cycle - I guess because it was in low level Apple code.