Firebase crashlytics reports many insight available crashes in my app - ios

Question

Below is my code
func getImageFrom(_ asset: PHAsset, completion: #escaping (UIImage) -> Void) {
var thumbnail = UIImage()
let imageManager = PHCachingImageManager()
let options = PHImageRequestOptions()
options.version = .current
let size = CGSize(width: 150.0, height: 150.0)
imageManager.requestImage(for: asset, targetSize: size, contentMode: .aspectFill,
options: nil) { (image, info) in
guard let img = image else { return }
thumbnail = img
}
completion(thumbnail)
}
I'm using this function to get an Image from PHAsset.
some time crash is reported at
thumbnail = img or at completion(thumbnail).
using this function in below code block
func getImageDataAndFindDupImages() {
var i = 0
var similarImages = [OSTuple<NSString, NSString>]()
similarImages = OSImageHashing.sharedInstance().similarImages(with: .high) { () -> OSTuple<NSString, NSData>? in
#if DEBUG
print(i)
#endif
var tuple = OSTuple<NSString, NSData>()
if self.tempArrAssets.count > 0 {
DispatchQueue.main.async {
self.lblNumberOfPhoto.text = R.string.localizable.scanning_photos_number("\(i+1)", "\(self.arrPhotoAssets.count)")
}
if !self.tempArrAssets.isEmpty {
let tempArrAsset = self.tempArrAssets.removeFirst()
self.getImageFrom(tempArrAsset) { (imageAsset) in
self.arrImageFromAsset.append(imageAsset)
if let imgData = imageAsset.pngData() {
tuple = (OSTuple<NSString, NSData>(first: NSString(string: "\(i)"), andSecond: imgData as NSData))
}
}
i += 1
return tuple
} else {
return nil
}
} else {
return nil
}
}
print("To make dup tuples:", Date().timeIntervalSince(self.date))
}
I'm using getImageFrom in getImageDataAndFindDupImages
This is a log for the crash
Crashed: com.apple.mobileslideshow.accessCallbacks
0 libobjc.A.dylib 0x18a874020 objc_retain + 16
1 Duplicate Cleaner 0x1001f0e80 closure #1 in DuplicatePhotoFinderVC.getImageDataAndFindDupImages() + 519 (DuplicatePhotoFinderVC.swift:519)
2 Duplicate Cleaner 0x1001f16a4 thunk for #escaping #callee_guaranteed () -> (#owned OSTuple<NSString, NSData>?) + 4338357924 (<compiler-generated>:4338357924)
3 CocoaImageHashing 0x1004f3514 -[OSSimilaritySearch similarImagesWithProvider:withHashDistanceThreshold:forImageStreamHandler:forResultHandler:] + 46 (OSSimilaritySearch.m:46)
4 CocoaImageHashing 0x1004f3924 -[OSSimilaritySearch similarImagesWithProvider:withHashDistanceThreshold:forImageStreamHandler:] + 95 (OSSimilaritySearch.m:95)
5 CocoaImageHashing 0x1004f28d0 -[OSImageHashing similarImagesWithProvider:withHashDistanceThreshold:forImageStreamHandler:] + 222 (OSImageHashing.m:222)
6 CocoaImageHashing 0x1004f27b0 -[OSImageHashing similarImagesWithHashingQuality:withHashDistanceThreshold:forImageStreamHandler:] + 201 (OSImageHashing.m:201)
7 CocoaImageHashing 0x1004f2734 -[OSImageHashing similarImagesWithHashingQuality:forImageStreamHandler:] + 190 (OSImageHashing.m:190)
8 Duplicate Cleaner 0x1001ee63c DuplicatePhotoFinderVC.getImageDataAndFindDupImages() + 316 (DuplicatePhotoFinderVC.swift:316)
9 Duplicate Cleaner 0x1001ee434 DuplicatePhotoFinderVC.fetchPhotosandCheckforDuplicate() + 146 (DuplicatePhotoFinderVC.swift:146)
10 Duplicate Cleaner 0x1001eea1c closure #1 in DuplicatePhotoFinderVC.checkForPermissionAndScanPhotos() + 162 (DuplicatePhotoFinderVC.swift:162)
11 Duplicate Cleaner 0x10021bdec thunk for #escaping #callee_guaranteed (#unowned PHAuthorizationStatus) -> () + 4338531820 (<compiler-generated>:4338531820)
12 Photos 0x195ff9098 __39+[PHPhotoLibrary requestAuthorization:]_block_invoke + 64
13 AssetsLibraryServices 0x19f048edc __79-[PLPrivacy _isPhotosAccessAllowedWithScope:forceHandler:accessAllowedHandler:]_block_invoke.14 + 520
14 AssetsLibraryServices 0x19f01486c __pl_dispatch_async_block_invoke + 36
15 libdispatch.dylib 0x18a7fe610 _dispatch_call_block_and_release + 24
16 libdispatch.dylib 0x18a7ff184 _dispatch_client_callout + 16
17 libdispatch.dylib 0x18a7ab404 _dispatch_lane_serial_drain$VARIANT$mp + 608
18 libdispatch.dylib 0x18a7abdf8 _dispatch_lane_invoke$VARIANT$mp + 420
19 libdispatch.dylib 0x18a7b5314 _dispatch_workloop_worker_thread + 588
20 libsystem_pthread.dylib 0x18a84eb88 _pthread_wqthread + 276
21 libsystem_pthread.dylib 0x18a851760 start_wqthread + 8
I'm not able to understand why I'm getting these crashes. If you have any knowledge please guide me.

Answer 1

You are passing nil to options parameter in the imageManager.requestImage(for:targetSize: contentMode:options:). If you pass nil as options, the method calls the completion block asyncrohonously. So there is a chance by the time your completion block gets called the method getImageFrom(: completion:) has exited and the local variable thumbnail has been destroyed(I am not talking about the UIImage object being destroyed but the variable which holds address of the UIImage itself). Then trying to set the thumbnail varibale which is no more on the stack, inside the block might be the reason there is a crash.
To solve your problem Create an instance of PHImageRequestOptions set its isSynchronous property to true like so.
let options = PHImageRequestOptions()
options.isSynchronous = true
Now pass this options as a parameter to the imageManager.requestImage(for:targetSize: contentMode:options:)
As a result your imageManager.requestImage(for:targetSize: contentMode:options:) will call the block synchronously meaning before the getImageFrom(: completion:) method exits and so the variable thumbnail is still alive on the stack to be used.
Hoping this should solve your problem.
PS: Take care you call the method getImageFrom(: completion:) in a background thread or your main thread will be frozen