Question

I’m trying to implement a better live(search as you type) contact search in my iPhone app. After doing some real device testing if found my current (non-threaded) implementation is just too slow. As far as I know there is no spotlight API for the iPhone. So I think the solution will have to be threaded so that it updates the results every x seconds instead of every keystroke. Are there any open source implementations I could build upon?

Thanks!

Answer 1

As far as I know there is no spotlight API for the iPhone.

You don’t need one. Here’s one way to go about it:

1. Put your contacts into a Core Data persistent store
2. Use NSFetchedResultsController to manage a result set
3. Use UISearchDisplayController to apply an NSPredicate on the result set in real time

The only threading I can see that you would need is a separate thread to populate the Core Data store with contacts.

Once you have a result set via NSFetchedResultsController, it is quite easy to apply a predicate. For example:

if ([self.searchBar.text length]) {
    _predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"(myContactName contains[cd] '%@')", self.searchBar.text]];
    [self.fetchedResultsController.fetchRequest setPredicate:_predicate];
}

NSError *error;
if (![self.fetchedResultsController performFetch:&error]) {
    // handle error...
}
NSLog(@"filtered results: %@", [self.fetchedResultsController fetchedObjects]);

will filter the result set [self.fetchedResultsController fetchedObjects] on the fly.