startAccessingSecurityScopedResource never returns success - objective-c

Question

I'm developing a sandboxed Mac App Store app which asks the user where to save files it downloads from elsewhere. I have this code to get the folder from the user (stripping out some error checking):
NSOpenPanel* openPanel = [NSOpenPanel openPanel];
[openPanel setAllowsMultipleSelection:NO];
[openPanel setCanChooseDirectories:YES];
[openPanel setResolvesAliases:YES];
NSInteger result = [openPanel runModal];
NSArray* urls = [openPanel URLs];
NSURL* folderURL = [urls objectAtIndex:0];
NSError* error;
NSData* bookmakeData = [folderURL bookmarkDataWithOptions:NSURLBookmarkCreationWithSecurityScope
includingResourceValuesForKeys:nil
relativeToURL:nil
error:&error];
_saveFolderBookmark = bookmakeData;
and when it comes time to move a file into this folder, I have this code:
BOOL isStale;
NSError* error;
NSURL* saveFolder = [NSURL URLByResolvingBookmarkData:_saveFolderBookmark
options:NSURLBookmarkCreationWithSecurityScope
relativeToURL:nil
bookmarkDataIsStale:&isStale
error:&error];
BOOL success = [saveFolder startAccessingSecurityScopedResource];
// Move the file somewhere else
NSWorkspace* workspace = [NSWorkspace sharedWorkspace];
NSInteger operationTag;
BOOL copied = [workspace performFileOperation:NSWorkspaceMoveOperation
source:[[self getDocumentsFolder] path]
destination:[saveFolder path]
files:[NSArray arrayWithObject:filename]
tag:&operationTag];
[saveFolder stopAccessingSecurityScopedResource];
Which is a lot of code to list to say that startAccessingSecurityScopedResource never returns success for me, either immediately after getting the ULR from NSOpenPanel or in a later run, with the bookmark data being saved in NSUserDefaults.
In the entitlements file, amongst other items, I have:
<key>com.apple.security.files.bookmarks.app-scope</key>
<true/>
Is there anything wrong with this code?

Answer 1

This one is very easy. You're resolving with NSURLBookmarkCreationWithSecurityScope instead of NSURLBookmarkResolutionWithSecurityScope. Just change that line and it should work.
(It may not work during the same session where you create the bookmark, when you already have access to the URL, because you're not supposed to call it in that case. But on later runs it should, of course, because that's the whole point.)

Answer 2

The correct solution has been given above, but I thought I’d add another possibility for those who are having the same symptom (startAccessingSecurityScopedResource never returning YES). Make sure that you are using the actual URL returned by Powerbox, which can (probably will) be different than the URL of the actual resource you are trying to access. For example, Powerbox will return a URL to a path, which you would use with startAccessingSecurityScopedResource to access a specific file underneath that directory.