How to use UIKeyCommand

I'm trying to select a row in a table view when a user presses the down arrow on a hardware keyboard. For now, I'm just trying to print a log, and I can't seem to get it to work. As per the other similar questions' answers, here's what I have so far:

- (NSArray *)keyCommands {
UIKeyCommand *downArrowKeyCommand = [UIKeyCommand keyCommandWithInput:UIKeyInputDownArrow
                                                        modifierFlags:0
                                                               action:@selector(hardwareKeyboardDownArrowPressed)];

return @[downArrowKeyCommand];
}

- (BOOL)canBecomeFirstResponder {
return YES;
}

- (void)hardwareKeyboardDownArrowPressed {

NSLog(@"Down arrow pressed on external keyboard");

}

All help is appreciated!

I don't know your particular mistake; it might be that you haven't added a (id)sender to your method. I figured how to do this. I'll add my code below:

- (BOOL)canBecomeFirstResponder {
    return YES;
}

- (NSArray *)keyCommands {
    return @[[UIKeyCommand keyCommandWithInput:UIKeyInputDownArrow modifierFlags:0 action:@selector(moveDownOneRow:) discoverabilityTitle:@"Select row down"],
             [UIKeyCommand keyCommandWithInput:UIKeyInputUpArrow modifierFlags:0 action:@selector(moveUpOneRow:) discoverabilityTitle:@"Select row up"]];
}

- (void)moveDownOneRow:(id)sender {
    NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

    if (indexPath == nil) {
        indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
    } else {
        if ((indexPath.row + 1) < [self.tableView numberOfRowsInSection:0]) {
            indexPath = [NSIndexPath indexPathForRow:indexPath.row+1 inSection:0];
        }
    }

    [self.tableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionMiddle];
}

- (void)moveUpOneRow:(id)sender {
    NSIndexPath *indexPath = [self.tableViewindexPathForSelectedRow];

    if (indexPath == nil) {
        indexPath = [NSIndexPath indexPathForRow:([self.tableView numberOfRowsInSection:0]-1) inSection:0];
    } else {
        if ((indexPath.row - 1) >= 0) {
            indexPath = [NSIndexPath indexPathForRow:indexPath.row-1 inSection:0];
        }
    }

    [self.tableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionMiddle];
}