Perform search through array in background thread? - objective-c

Question

I have a pretty large array I get from my database peopleArray that consists of all the users of my app. This array is used for searching for friends. My problem is, when the user begins to type in the search bar the app often freezes for a moment before display the searched user.
#pragma mark - SEARCH BAR
- (void) filterContententForSearchText: (NSString *) searchText scope:(NSString *) scope{
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"%K beginsWith[cd] %#",#"Name", searchText ];
self.searchArray = [self.peopleArray filteredArrayUsingPredicate:predicate];
}
- (BOOL) searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString{
[self filterContententForSearchText:searchString scope:[[self.searchDisplayController.searchBar scopeButtonTitles] objectAtIndex:[self.searchDisplayController.searchBar selectedScopeButtonIndex]]];
return YES;
}
- (void) searchDisplayControllerDidEndSearch:(UISearchDisplayController *)controller{
[self.tableView reloadData];
}
I would like to do this in the background so I can put a UIActivityIndicator in the tableView as it loads but am not sure where or how to implement which method in the background.

Answer 1

First of all, I would suggest using a timer so that you don't reload the users on EVERY keypress. I do that like this:
//I put this in my private #interface
#property (nonatomic, strong) NSTimer *searchTimer;
//Then we have the method called on keypress
- (void)whateverMethodIsCalledOnKeypress {
[self.searchTimer invalidate];
self.searchTimer = nil;
//put some logic that returns out of the function for empty strings etc. here
self.searchTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(runSearch) userInfo:nil repeats:NO];
}
- (void)runSearch {
//do whatever you need to run the search this way
//it's only ever done at most once per second
//so fast typists don't overload the processor
}
And here is some code to do an async filtering.
//Show your activity indicator
dispatch_async(dispatch_get_global_queue(0,0), ^{
//call whatever you need to do on the filtering here
dispatch_async(dispatch_get_main_queue(), ^{
//Hide your activity indicator
[self.tableView reloadData];
});
});