Reading files with UIDocumentPickerViewController in a Mac Catalyst app requires read/write entitlement?

Question

I have this code in a UIViewController that confirms to UIDocumentPickerDelegate:

- (void)openTextFilePicker {
    NSArray *UTIs = [NSArray arrayWithObjects:@"public.text", nil];
    [self openFilePicker:UTIs];
}

- (void)openFilePicker:(NSArray *)UTIs {
    UIDocumentPickerViewController *documentPicker = [[UIDocumentPickerViewController alloc] initWithDocumentTypes:UTIs inMode:UIDocumentPickerModeImport];
    documentPicker.delegate = self;
    documentPicker.popoverPresentationController.barButtonItem = self.importButton;
    [self presentViewController:documentPicker animated:TRUE completion:nil];
}

- (void)documentPicker:(UIDocumentPickerViewController *)controller didPickDocumentAtURLs:(NSArray<NSURL *> *)urls {
    [self documentPicker:controller didPickDocumentAtURL:[urls firstObject]];
}

- (void)documentPicker:(UIDocumentPickerViewController *)controller didPickDocumentAtURL:(NSURL *)url {
    NSLog(@"picked document %@", url);
}

- (void)documentPickerWasCancelled:(UIDocumentPickerViewController *)controller {
    NSLog(@"cancelled");
}

This allows users to select a file anywhere on their system and import its contents into the app. It works if I have the App Sandbox > User Selected File capability set to Read/Write. But I'm only reading data in from the file, I don't need to update the file or save anything outside of the sandbox. So I changed the capability to Read Only, but then I get this error in the console, and didPickDocumentsAtURLs isn't called:

Failed to create an FPSandboxingURLWrapper for [path]. Error: Error Domain=NSPOSIXErrorDomain Code=1 "couldn't issue sandbox extension com.apple.app-sandbox.read-write for '[path]': Operation not permitted"

Does that seem right, or should I be able to read files with just the Read Only entitlement? It's easy enough to switch it to Read/Write if needed, but my first submission was rejected for using unnecessary entitlements, and I want to be prepared to justify this to the review team if it is in fact needed.

odlh odlh · Accepted Answer · 2021-01-18T01:23:32

For anyone searching for this, I did not get granted app approval by stating my case - instead I was forced to find the following solution - which uses a UIDocumentBrowserViewController (Read only!) vs a UIDocumentPickerViewController (which requires read-write)

import Foundation
import UIKit

extension ViewController: UIDocumentBrowserViewControllerDelegate, UIDocumentPickerDelegate {
    
    @objc func presentDocumentPicker() {
        
        if operatingSystem == .macintosh {
            let documentPicker = UIDocumentBrowserViewController(forOpening: [.pdf])
            documentPicker.delegate = self
            documentPicker.allowsDocumentCreation = false
            documentPicker.allowsPickingMultipleItems = false
            // Present the document picker.
            present(documentPicker, animated: true, completion: nil)
        } else {
            let documentsPicker = UIDocumentPickerViewController(forOpeningContentTypes: [.pdf])
            documentsPicker.delegate = self
            documentsPicker.allowsMultipleSelection = false
            documentsPicker.modalPresentationStyle = .fullScreen
            self.present(documentsPicker, animated: true, completion: nil)
        }

    }
    
    
    func documentBrowser(_ controller: UIDocumentBrowserViewController, didPickDocumentsAt documentURLs: [URL]) {
        guard let url = documentURLs.first, url.startAccessingSecurityScopedResource() else { return }
        defer {
            DispatchQueue.main.async {
                url.stopAccessingSecurityScopedResource()
            }
        }
        debugPrint("[DocumentPicker] Selected Item with URL : ", url)
        controller.dismiss(animated: true)
    }
    
    public func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
        guard let url = urls.first, url.startAccessingSecurityScopedResource() else { return }
        defer {
            DispatchQueue.main.async {
                url.stopAccessingSecurityScopedResource()
            }
        }
        debugPrint("[DocumentPicker] Selected Item with URL : ", url)
        controller.dismiss(animated: true)
    }

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

Reading files with UIDocumentPickerViewController in a Mac Catalyst app requires read/write entitlement?

2 Answers