Save DocumentPicker URL for further use

Hello, I'm having trouble saving the value of an NSURL object.

The code bellow is used in a c++ project, however, this issue shouldn't be exclusive to this scenario.

I want to use document picker, only to choose a file and get its url, which I would use on c++ side to read/write data. That I've managed to do successfully, by passing the url to c++ side by calling FileWasPicked(std::string) c++ method.

However, since document picker allows us to choose files only from public folders, I need to call start/stopAccessingSecurityScopedResource, and to call them I need to pass an NSURL object, that I get from the document picker. I call startAccessingSecurityScopedResource method before leaving didPickDocumentsAtURLs method, however I can't do that with the stopAccessingSecurityScopedResource.

I've tried to save the NSURL we get from document picker in a class variable @property NSURL *m_LastUsedURL;, however it's value changes after leaving didPickDocumentsAtURLs method. My guess, is that after leaving the before mention method, the value of the object that we save a pointer to gets deinitialized. Passing the string value back from c++ and converting it to an NSURL object doesn't work either.

Is there any way to save NSURL object value in this case, or call the stopAccessingSecurityScopedResource method in a different manner?

I attach my current code:

@implementation DocumentPicker //In a DocumentPicker.mm file

//We call this method from c++, to open document picker
- (void)openDocumentPicker:(NSString*)pickerType //We pass the picker type from c++
{
    //Find the current app window, and its view controller object
    UIApplication* app = [UIApplication sharedApplication];
    UIWindow* rootWindow = app.windows[0];
    UIViewController* rootViewController = rootWindow.rootViewController;
    
    UIDocumentPickerViewController *documentPicker = [[UIDocumentPickerViewController alloc] initWithDocumentTypes:@[pickerType] inMode:UIDocumentPickerModeOpen];
    
    documentPicker.delegate = self;

    documentPicker.modalPresentationStyle = UIModalPresentationFormSheet;

    [rootViewController presentViewController:documentPicker animated:YES completion:nil];
}

//Callback, that gets called after user successfully chooses a file
- (void)documentPicker:(UIDocumentPickerViewController *)controller didPickDocumentsAtURLs:(NSArray<NSURL *> *)urls
{
    //Start accessing file, that the user have picked
    if ( [urls[0] startAccessingSecurityScopedResource] )
    {
        _m_LastUsedURL = urls[0];
        //Pass the url and exit this method, to do actions in c++
        GlobalCppClass->FileWasPicked(urls[0].absoluteString.UTF8String);
    }
    else
    {
        NSLog(@"startAccessingSecurityScopedResource failed");
    }
}

//This would be called, after we finish reading the file in c++
-(void)stopAccesingFile
{
    [_m_LastUsedURL stopAccessingSecurityScopedResource];
}

@end