iOS: Do not back up attribute?

Question

Our app has recently been rejected for violating iOS Data Storage Guidelines about backing up files on iCloud.

I must mark data with the do not back up attribute.

I'm storing all my important data in SQLite databases and my user preferences in UserDefaults.plist. Do I have to mark my database.sqlite files as do no back up?

I asked the reviewer if I were to disable iCloud in my AppID would it help my situation, and the response was cryptic and didn't really give me a yes or no answer.

Nothing in my app really needs to be backed up, can I just disable iCloud support in my AppID and not have to worry about marking files as do not back up??

Here is the reviewer's response:

2.23

We also found that your app does not follow the iOS Data Storage Guidelines, which is required per the App Store Review Guidelines.

In particular, we found that on launch and/or content download, your app stores 4 MB. To check how much data your app is storing:

• Install and launch your app
• Go to Settings > iCloud > Storage & Backup > Manage Storage
• If necessary, tap "Show all apps"
• Check your app's storage

The iOS Data Storage Guidelines indicate that only content that the user creates using your app, e.g., documents, new files, edits, etc., should be backed up by iCloud.

Temporary files used by your app should only be stored in the /tmp directory; please remember to delete the files stored in this location when the user exits the app.

Data that can be recreated but must persist for proper functioning of your app - or because customers expect it to be available for offline use - should be marked with the "do not back up" attribute. For NSURL objects, add the NSURLIsExcludedFromBackupKey attribute to prevent the corresponding file from being backed up. For CFURLRef objects, use the corresponding kCFURLIsExcludedFromBackupKey attribute.

For more information, please see Technical Q&A 1719: How do I prevent files from being backed up to iCloud and iTunes?.

It is necessary to revise your app to meet the requirements of the iOS Data Storage Guidelines. For discrete code-level questions, you may wish to consult with Apple Developer Technical Support. Please be sure to:

• include the complete details of your rejection issues
• prepare any symbolicated crash logs, screenshots, and steps to reproduce the issues for when the DTS engineer follows up.

Answer 1

Basically, it depends on the kind of data you are storing.

If the data can be regenerated (when a user install the app on another device, for instance), then it should not be backed up.

Otherwise, iCloud backup is OK, as the user will expect his data to be available, even on another device.

In the first scenario, you have basically two ways of achieving this...

Either you use NSURL to set the kCFURLIsExcludedFromBackupKey on your files, either you store them in a location that won't be backed-up, like <Application_Home>/Library/Caches. Note that the second solution is the better, IMHO.

For info, kCFURLIsExcludedFromBackupKey can be used this way:

NSURL * fileURL;

fileURL = [ NSURL fileURLWithPath: @"some/file/path" ];

[ fileURL setResourceValue: [ NSNumber numberWithBool: YES ] forKey: NSURLIsExcludedFromBackupKey error: nil ];

For the second scenario, sometimes Apple reviewers think your data can be re-generated, when it's not. Then you'll have to explain why the data has to be backed-up.

Answer 2

You can call the following function to pass the path of your "map.sqlite" as NSURL:

NSURL *url = [NSURL fileURLWithPath:yourSQLitePath];
[self addSkipBackupAttributeToItemAtURL:url];
The function is provided in Apple as:

- (BOOL)addSkipBackupAttributeToItemAtURL:(NSURL *)URL
{
    assert([[NSFileManager defaultManager] fileExistsAtPath: [URL path]]);

    NSError *error = nil;
    BOOL success = [URL setResourceValue: [NSNumber numberWithBool: YES]
                              forKey: NSURLIsExcludedFromBackupKey error: &error];
    if(!success){
        NSLog(@"Error excluding %@ from backup %@", [URL lastPathComponent], error);
    }
    return success;
}