I have discovered a gap in my understanding of user selected URLs in iOS, and I would be grateful if someone can put me right please.
My understanding is that a URL selected by a user can be accessed by calling url.startAccessingSecurityScopedResource() call. Subsequently a call to stopAccessingSecurityScopedResource() is made to avoid sandbox memory leaks.
Furthermore, the URL can be saved as a bookmark and reconstituted when the app is run again to avoid re-asking permission from the user.
So far so good.
However, I have discovered that a URL retrieved from a bookmark can be accessed without the call to url.startAccessingSecurityScopedResource(). This seems contrary to what the documentation says here
So my question is (assuming this is not a bug) why not save and retrieve the URL immediately in order to avoid having to make any additional calls to url.startAccessingSecurityScopedResource?
Bill Aylward
You can copy and paste the code below into a new iOS project to illustrate this. Having chosen a folder, the 'Summarise folder without permission' button fails as expected, but once the 'Retrieve URL from bookmark' has been pressed, it works fine.
import SwiftUI
import UniformTypeIdentifiers
struct ContentView: View {
@AppStorage("bookmarkData") private var bookmarkData: Data?
@State private var showFolderPicker = false
@State private var folderUrl: URL?
@State private var folderReport: String?
var body: some View {
VStack(spacing: 20) {
Text("Selected folder: \(folderUrl?.lastPathComponent ?? "None")")
Text("Contents: \(folderReport ?? "Unknown")")
Button("Select folder") {
showFolderPicker.toggle()
}
Button("Deselect folder") {
folderUrl = nil
folderReport = nil
bookmarkData = nil
}
.disabled(folderUrl == nil)
Button("Retrieve URL from bookmark") {
retrieveFolderURL()
}
.disabled(bookmarkData == nil)
Button("Summarise folder with permission") {
summariseFolderWithPermission(true)
}
.disabled(folderUrl == nil)
Button("Summarise folder without permission") {
summariseFolderWithPermission(false)
}
.disabled(folderUrl == nil)
}
.padding()
.fileImporter(
isPresented: $showFolderPicker,
allowedContentTypes: [UTType.init("public.folder")!],
allowsMultipleSelection: false
) { result in
switch result {
case .success(let urls):
if let selectedUrl = urls.first {
print("Processing folder: \(selectedUrl)")
processFolderURL(selectedUrl)
}
case .failure(let error):
print("\(error.localizedDescription)")
}
}
.onAppear() {
guard folderUrl == nil else { return }
retrieveFolderURL()
}
}
func processFolderURL(_ selectedUrl: URL?) {
guard selectedUrl != nil else { return }
// Create and save a security scoped bookmark in AppStorage
do {
guard selectedUrl!.startAccessingSecurityScopedResource() else { print("Unable to access \(selectedUrl!)"); return }
// Save bookmark
bookmarkData = try selectedUrl!.bookmarkData(options: .minimalBookmark, includingResourceValuesForKeys: nil, relativeTo: nil)
selectedUrl!.stopAccessingSecurityScopedResource()
} catch {
print("Unable to save security scoped bookmark")
}
folderUrl = selectedUrl!
}
func retrieveFolderURL() {
guard let bookmarkData = bookmarkData else {
print("No bookmark data available")
return
}
do {
var isStale = false
let url = try URL(
resolvingBookmarkData: bookmarkData,
options: .withoutUI,
relativeTo: nil,
bookmarkDataIsStale: &isStale
)
folderUrl = url
} catch {
print("Error accessing URL: \(error.localizedDescription)")
}
}
func summariseFolderWithPermission(_ permission: Bool) {
folderReport = nil
print(String(describing: folderUrl))
guard folderUrl != nil else { return }
if permission { print("Result of access requrest is \(folderUrl!.startAccessingSecurityScopedResource())") }
do {
let contents = try FileManager.default.contentsOfDirectory(atPath: folderUrl!.path)
folderReport = "\(contents.count) files, the first is: \(contents.first!)"
} catch {
print(error.localizedDescription)
}
if permission { folderUrl!.stopAccessingSecurityScopedResource() }
}
}
Selecting any option will automatically load the page