使用uisearchbar搜索很慢,并且阻塞了主线程

我有一张3000多个条目的桌子,搜索速度很慢。

目前,我所做的就像在“TableSearch”示例代码中一样(但没有范围)

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
{
    [self filterContentForSearchText: searchString];

    // Return YES to cause the search result table view to be reloaded.
    return YES;
}

filterContentForsearchText方法如下:

- (void) filterContentForSearchText:(NSString*)searchText
{
// Update the filtered array based on the search text

// First clear the filtered array.
[filteredListContent removeAllObjects]; 

// Search the main list whose name matches searchText
// add items that match to the filtered array.
if (fetchedResultsController.fetchedObjects)
{
    for (id object in fetchedResultsController.fetchedObjects)
    {
        NSString* searchTarget = [tableTypeDelegate getStringForSearchFilteringFromObject:object];

        if ([searchTarget rangeOfString:searchText
                options:(NSCaseInsensitiveSearch|NSDiacriticInsensitiveSearch)].location != NSNotFound)
        {
                [filteredListContent addObject:object];
        }
    }
}
}

我的问题是双重的:

• 如何使搜索过程更快?
• 如何阻止搜索阻塞主线程?也就是说,停止它,防止用户键入更多字符。

在第二部分中,我尝试了“PerformSelector:WithObject:AfterDelay:”和“CancelPreviousPerformRequests…”,但没有成功。我怀疑我需要使用线程来代替它,但是我对它没有太多的经验。