Question

I have a huge tree of files and dirs for cache in my document directory.

As recommended, I’m going to use NSURLIsExcludedFromBackupKey for preventing iTunes from saving this data with the app.

Can I use it once on my root directory URL, as

[rootDirectoryURL setResourceValue:[NSNumber numberWithBool:YES] forKey:@"NSURLIsExcludedFromBackupKey" error:&error];

Or will I have to call it for each file?

Answer 1

Yup, you can pass it a NSURL of the directory you want excluded.

- (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;
}

And you can test any files if in doubt using

id flag = nil;
[URL getResourceValue: &flag
               forKey: NSURLIsExcludedFromBackupKey error: &error];
NSLog (@"NSURLIsExcludedFromBackupKey flag value is %@", flag)