Problems with saving an image from UIDocumentPickerViewController / .stopAccessingSecurityScopedResource()

Question

I have a viewcontroller that presents my custom ImagePicker class. One of the presented options is to select an image from 'Files', using UIDocumentPickerViewController. Picking an image works fine, but i want to close the security resources conform the recommendations.

ProjectimagePicker {
(...)
            let documentsPicker = UIDocumentPickerViewController(documentTypes: ["public.image", "public.jpeg", "public.png"], in: .open)
            documentsPicker.delegate = self
            documentsPicker.allowsMultipleSelection = false
            documentsPicker.modalPresentationStyle = .fullScreen
            self.presentationController?.present(documentsPicker, animated: true, completion: nil)
}

//MARK: - Ext. Delegate DocumentPicker
extension ProjectImagePicker: UIDocumentPickerDelegate {
    public func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
        guard controller.documentPickerMode == .open, let url = urls.first, url.startAccessingSecurityScopedResource() else { return }
        defer {
            DispatchQueue.main.async {
                url.stopAccessingSecurityScopedResource()
            }
             }

        guard let image = UIImage(contentsOfFile: url.path) else { return }
        self.delegate?.didSelect(image: image)
        controller.dismiss(animated: true)
    }

    public func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
        controller.dismiss(animated: true)
    }
}

And in the viewController that called the picker class:

//MARK: - Delegate ProjectImagePicker
extension ProjectDetailsViewController: ProjectImagePickerDelegate {
    func didSelect(image: UIImage?) {
        if let image  = image {
            selectedImage = image
            projectImageView.image = image
        }
    }
}

Part of the problem I circumvent by wrapping a dispatch call around stopAccessingSecurityScopedResource(). The image gets send back (delegate) and presented in the viewController. But when I eventually save (write to documents directory) my project and that image (selectedImage), I get the security error

2020-05-08 13:54:04.429936+0200 ProjectS[3482:1339708] [ProjectS] createDataWithMappedFile:1524:  'open' failed '/private/var/mobile/Library/Mobile Documents/com~apple~CloudDocs/10.JPEG'  error = 1 (Operation not permitted)

So, apparently the image is still referencing the URL from the Documents picker. I could try and save the image temporarily in the didPickDocumentsAt method, but that seems ugly. Or I can omit calling stopAccessingSecurityScopedResource() all together, but that may cause problems? Any ideas on how to handle this the best possible way ?

score 0 · Answer 1 · answered May 08 '20 at 12:30

If I update my code for didPickDocumentsAt in the way that I make a copy of the image, all works as intended

//MARK: - Ext. Delegate DocumentPicker
extension ProjectImagePicker: UIDocumentPickerDelegate {
    public func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
        guard controller.documentPickerMode == .open, let url = urls.first, url.startAccessingSecurityScopedResource() else { return }
        defer {
            DispatchQueue.main.async {
                url.stopAccessingSecurityScopedResource()
            }
             }

        //Need to make a new image with the jpeg data to be able to close the security resources!
        guard let image = UIImage(contentsOfFile: url.path), let imageCopy = UIImage(data: image.jpegData(compressionQuality: 1.0)!) else { return }

        self.delegate?.didSelect(image: imageCopy)
        controller.dismiss(animated: true)
    }

Good solution, or better ideas?

Problems with saving an image from UIDocumentPickerViewController / .stopAccessingSecurityScopedResource()

1 Answers1