NSCocoaErrorDomain Code=257 File Permission - swift

Question

While trying to get a file inside a Swift UI App using a UIViewControllerRepresentable wrapping an UIDocumentPickerViewController, I ran into a very weird behaviour:
Running the app on the simulator works as expected. Running the app on a physical device however would not return the files. Instead it would throw this error: Error Domain=NSCocoaErrorDomain Code=257 "The file “grile.doc” couldn’t be opened because you don’t have permission to view it."
Debugging, I managed to find that the code block causing this error to be thrown on the physical device isn't the actual accessing of the file, instead it's trying to get the file size that throws.
What am I doing wrong here, that makes this Representable work just fine on a simulator but not work on a physical device?
I have already tried using the FileManager approach to get file size, same thing happens. I also tried copying the file to a temp location with FileManager, that also throws the same error.
import Foundation
import SwiftUI
import UniformTypeIdentifiers
struct FilePicker: UIViewControllerRepresentable {
// MARK: - Properties
var didPickFileURL: ((URL) -> Void)
var didPickFileOverFileSizeLimit: (() -> Void)
// MARK: - UIViewController Wrapper Methods
func makeUIViewController(context: Context) -> UIDocumentPickerViewController {
let picker = UIDocumentPickerViewController(forOpeningContentTypes: [UTType("public.item")!])
picker.allowsMultipleSelection = false
picker.delegate = context.coordinator
return picker
}
func updateUIViewController(_ uiViewController: UIDocumentPickerViewController, context: Context) {
}
func makeCoordinator() -> Coordinator {
return FilePicker.Coordinator(parent: self)
}
// MARK: - Coordinator
class Coordinator: NSObject, UIDocumentPickerDelegate {
// MARK: - Coordinator Properties
var parent: FilePicker
// MARK: - Coordinator Init
init(parent: FilePicker) {
self.parent = parent
}
// MARK: - Coordinator UIDocument Delegate
func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
guard let url = urls.first else { return }
do {
let resources = try url.resourceValues(forKeys:[.fileSizeKey])
let fileSize = Double(resources.fileSize!)
// check if the file size is bigger than the limit per attachment
if fileSize.convertBytesToMegabytes() < 10 {
self.parent.didPickFileURL(url)
} else {
self.parent.didPickFileOverFileSizeLimit()
}
} catch {
print("Error: \(error)")
}
}
}
}
The conversion extension:
extension Double {
func convertBytesToMegabytes() -> Double {
let kilobytes = self / 1024
let megabytes = kilobytes / 1024
return megabytes
}
}

Answer 1

I've had issues as well. If you look at the URL to your document you might try:
url.startAccessingSecurityScopedResource()
If that returns true you will also need to call:
url.stopAccessingSecurityScopedResource()