NSFetchRequest * fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Contact"];
// Configure the request's entity, and optionally its predicate.
NSSortDescriptor * sortByFirstLetter = [[NSSortDescriptor alloc] initWithKey:@"firstLetter"
                                                                   ascending:YES
                                                                    selector:@selector(localizedCaseInsensitiveCompare:)];
NSSortDescriptor * sortByName = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];
[fetchRequest setSortDescriptors:@[sortByFirstLetter, sortByName]];

NSFetchedResultsController * controller = <#Fetched results controller#>

RITableDataSource * dataSource = [RITableDataSource dataSourceWithFetchedResultsController:controller];
[dataSource setReusableIdentifierBlock:^NSString *(NSIndexPath * indexPath) {
    return <#Cell reusable identifier#>;
}];
[dataSource setConfigureCellBlock:^(UITableViewCell * cell, NSIndexPath * indexPath, id object) {
    // Configurate cell here
}];
dataSource.tableView = self.tableView;