Possible to persist HKQueryAnchor in NSUserDefaults?

Question

So I'm a bit dismayed that Apple has replaced a transparent, easy-to-handle NSUInteger with an HKQueryAnchor but has not provided an easy way to persist that HKQueryAnchor. Has anyone found a good way to do this with NSUserDefaults? The only persistence method I have seen is an archiver to a local file, but my app persists everything in NSUserDefaults, and I'd like to keep it that way if possible. Is there a reliable way to store an HKQueryAnchor this way?

Answer 1

You can convert it to NSData using NSKeyedArchiver and store that in the user defaults.

To store:

NSData *data = [NSKeyedArchiver archivedDataWithRootObject:anchor];
[[NSUserDefaults standardUserDefaults] setObject:data forKey:@"AnchorData"];

To retrieve:

NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:@"AnchorData"];
HKQueryAnchor *anchor = [NSKeyedUnarchiver unarchiveObjectWithData:data];