Memleak with UIDocumentPickerViewController via SwiftUI - ios

Question

The application is built for iOS. I want user to choose a file from it's directory and get the url of chosen one. Apple recommends UIDocumentPickerViewController to solve this issue. I wrapped it in UIViewControllerRepresentable, so it is the first place, where I can mistake
import SwiftUI
import MobileCoreServices
struct DocumentPickerView: UIViewControllerRepresentable {
func makeCoordinator() -> Coordinator {
return DocumentPickerView.Coordinator()
}
func makeUIViewController(context: Context) -> UIDocumentPickerViewController {
let picker = UIDocumentPickerViewController(documentTypes: [String(kUTTypeItem)], in: .import)
picker.allowsMultipleSelection = false
picker.delegate = context.coordinator
return picker
}
func updateUIViewController(_ uiViewController: UIDocumentPickerViewController, context: Context) {
}
class Coordinator: NSObject, UIDocumentPickerDelegate {
func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
print("url: \(urls[0].absoluteString )")
}
}
}
struct ContentView: View {
#State var showPicker = false
var body: some View {
Button(action: {
self.showPicker.toggle()
}, label: {
Text("Push me")
})
.sheet(isPresented: self.$showPicker) {
DocumentPickerView()
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
The reason I think that there is a problem is that Xcode instruments show that memory leaks, here the trace:
32 Bytes 100.0% 1 start
32 Bytes 100.0% 1 main
32 Bytes 100.0% 1 UIApplicationMain
32 Bytes 100.0% 1 GSEventRunModal
32 Bytes 100.0% 1 CFRunLoopRunSpecific
32 Bytes 100.0% 1 __CFRunLoopRun
32 Bytes 100.0% 1 __CFRunLoopDoObservers
32 Bytes 100.0% 1 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__
32 Bytes 100.0% 1 _afterCACommitHandler
32 Bytes 100.0% 1 _cleanUpAfterCAFlushAndRunDeferredBlocks
32 Bytes 100.0% 1 _runAfterCACommitDeferredBlocks
32 Bytes 100.0% 1 __56-[UIPresentationController runTransitionForCurrentState]_block_invoke.478
32 Bytes 100.0% 1 _UIViewControllerTransitioningRunCustomTransition
32 Bytes 100.0% 1 +[UIView(Animation) _setAlongsideAnimations:toRunByEndOfBlock:]
32 Bytes 100.0% 1 ___UIViewControllerTransitioningRunCustomTransition_block_invoke.648
32 Bytes 100.0% 1 +[UIInputResponderController _pinInputViewsForInputResponderController:onBehalfOfResponder:duringBlock:]
32 Bytes 100.0% 1 ___UIViewControllerTransitioningRunCustomTransition_block_invoke_2
32 Bytes 100.0% 1 -[UIViewControllerBuiltinTransitionViewAnimator animateTransition:]
32 Bytes 100.0% 1 -[UITransitionView transition:fromView:toView:removeFromView:]
32 Bytes 100.0% 1 -[UITransitionView _startTransition:withDuration:]
32 Bytes 100.0% 1 +[UIView(UIViewAnimationWithBlocks) conditionallyAnimate:withAnimation:layout:completion:]
32 Bytes 100.0% 1 __50-[UITransitionView _startTransition:withDuration:]_block_invoke.169
32 Bytes 100.0% 1 +[UIView(UIViewAnimationWithBlocks) animateWithDuration:delay:options:animations:completion:]
32 Bytes 100.0% 1 +[UIView(UIViewAnimationWithBlocks) _setupAnimationWithDuration:delay:view:options:factory:animations:start:animationStateGenerator:completion:]
32 Bytes 100.0% 1 +[UIViewAnimationState popAnimationState]
32 Bytes 100.0% 1 -[UIViewAnimationState pop]
32 Bytes 100.0% 1 -[UIViewAnimationState _runAlongsideAnimations]
32 Bytes 100.0% 1 __63+[UIView(Animation) _setAlongsideAnimations:toRunByEndOfBlock:]_block_invoke
32 Bytes 100.0% 1 -[_UIViewControllerTransitionContext __runAlongsideAnimations]
32 Bytes 100.0% 1 -[_UIViewControllerTransitionCoordinator _applyBlocks:releaseBlocks:]
32 Bytes 100.0% 1 __54-[_UISheetPresentationController transitionWillBegin:]_block_invoke.345
32 Bytes 100.0% 1 +[UIView(Animation) performWithoutAnimation:]
32 Bytes 100.0% 1 __54-[_UISheetPresentationController transitionWillBegin:]_block_invoke_2
32 Bytes 100.0% 1 -[_UISheetLayoutInfo _layout]
32 Bytes 100.0% 1 -[_UISheetPresentationController _sheetLayoutInfoLayout:]
32 Bytes 100.0% 1 -[UIView(Hierarchy) layoutBelowIfNeeded]
32 Bytes 100.0% 1 CA::Layer::layout_if_needed(CA::Transaction*)
32 Bytes 100.0% 1 -[CALayer layoutSublayers]
32 Bytes 100.0% 1 -[UIView(CALayerDelegate) layoutSublayersOfLayer:]
32 Bytes 100.0% 1 #objc _UIHostingView.layoutSubviews()
32 Bytes 100.0% 1 _UIHostingView.layoutSubviews()
32 Bytes 100.0% 1 ViewRendererHost.render(interval:updateDisplayList:)
32 Bytes 100.0% 1 closure #1 in ViewRendererHost.render(interval:updateDisplayList:)
32 Bytes 100.0% 1 closure #1 in closure #1 in ViewRendererHost.render(interval:updateDisplayList:)
32 Bytes 100.0% 1 ViewGraph.updateOutputs(at:)
32 Bytes 100.0% 1 closure #1 in ViewGraph.updateOutputs(at:)
32 Bytes 100.0% 1 ViewGraph.runTransaction(in:)
32 Bytes 100.0% 1 AG::Subgraph::update(unsigned int)
32 Bytes 100.0% 1 AG::Graph::update_attribute(unsigned int, bool)
32 Bytes 100.0% 1 AG::Graph::UpdateStack::update()
32 Bytes 100.0% 1 partial apply
32 Bytes 100.0% 1 protocol witness for static UntypedAttribute._update(_:graph:attribute:) in conformance PlatformViewChild<A>
32 Bytes 100.0% 1 PlatformViewChild.update(context:)
32 Bytes 100.0% 1 closure #1 in PlatformViewChild.update(context:)
32 Bytes 100.0% 1 swift_weakInit
32 Bytes 100.0% 1 swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1> >::formWeakReference()
32 Bytes 100.0% 1 operator new(unsigned long)
32 Bytes 100.0% 1 malloc
With multiple calls at allocation I have such entities that have lost theirs memory:
Category Persistent # Persistent # Transient Total Bytes
UIDocumentBrowserViewController 22,50 KiB 15 0 22,50 KiB
DOCRemoteViewController 22,50 KiB 15 0 22,50 KiB
_UIResilientRemoteViewContainerViewController 13,36 KiB 15 0 13,36 KiB
_UIRemoteView 6,80 KiB 15 0 6,80 KiB
_UISizeTrackingView 6,56 KiB 15 0 6,56 KiB
DOCRemoteBarButtonTrackingView 5,62 KiB 15 0 5,62 KiB
DOCConfiguration  2,58 KiB 15 0 2,58 KiB
DOCRemoteContext 1,88 KiB 15 0 1,88 KiB
_UIViewServiceInterface 1,41 KiB 15 0 1,41 KiB
__NSXPCInterfaceProxy__NSExtensionContextVending 1,17 KiB 15 0 1,17 KiB
UISystemDefaultTextInputAssistantItem 1,17 KiB 15 0 1,17 KiB
UIKeyboardBIUImageGenerator 960 Bytes 15 0 960 Bytes
_UIViewServiceReplyControlProxy 720 Bytes 15 0 720 Bytes
Swift.__SwiftDeferredNSArray 480 Bytes 15 0 480 Bytes
DOCRemoteBarButton 480 Bytes 15 0 480 Bytes
NSWeakObjectValue 480 Bytes 15 0 480 Bytes
_UIRemoteViewService 480 Bytes 15 0 480 Bytes
_UIViewServiceImplicitAnimationEncodingProxy 480 Bytes 15 0 480 Bytes
DOCWeakProxy 240 Bytes 15 0 240 Bytes
UPD:
I just started feedback to solve this problem, but I found that there are no similar problems, so if you have the same one please report too

Answer 1

This is definitely Apple's bug, so worth submitting feedback to them.
Meanwhile here is a safe workaround applicable for majority of use-cases. Tested with Xcode 11.4 / iOS 13.4. The idea is to use shared document picker instance and just reconfigure it on every call.
struct DocumentPickerView: UIViewControllerRepresentable {
static let picker = UIDocumentPickerViewController(documentTypes: [String(kUTTypeItem)], in: .import)
func makeUIViewController(context: Context) -> UIDocumentPickerViewController {
Self.picker.allowsMultipleSelection = false
Self.picker.delegate = context.coordinator
return Self.picker
}
// ... other code no changes