Create index for UITableView from an NSArray

Question

I've read that the best way of creating an index (the a-z at the side of a uitableview) is to set up an array of nsdictionaries, where each dictionary corresponds to a section, and a rowValue key contains an array of the rows.

NSDictionary
    headerTitle => ‘A’
    rowValues => {”Aardvark”, “Ape”, “Aquaman”}
NSDictionary
    headerTitle => ‘B’
    rowValues => {”Bat”, “Boot”, “Bubbles”} etc

But how can this be created from an array of all the row titles - {”Aardvark”, “Ape”, “Aquaman”, ”Bat”, “Boot”, “Bubbles”, "Cat", "Cabbage" etc} ...?

Answer 1

#pragma mark -
#pragma mark View lifecycle
- (void)viewDidLoad
{
    [super viewDidLoad];
    NSMutableArray *temp = [[NSMutableArray alloc] init];
    NSMutableArray *temp2 = [[NSMutableArray alloc] init];
    for(int i = 0; i < tableListArray.count; i++)
    {
        NSString *string = [tableListArray objectAtIndex:i];
        NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
        [dict setObject:string forKey:@"Name"];
        [dict setObject:[NSNumber numberWithInt:i] forKey:@"ID"];
        NSString *firstString = [string substringToIndex:1];
        if([temp2 containsObject:firstString] == NO || temp2.count == 0)
        {
            if(temp2.count != 0)
            {
                [temp addObject:temp2];
                [temp2 release];
                temp2 = [[NSMutableArray alloc] init];
            }
            [temp2 addObject:firstString];
        }
        [temp2 addObject:dict];
        [dict release];
    }
    [temp addObject:temp2];
    detailListArray = [[NSArray alloc] initWithArray:temp];
    [temp release];
    [temp2 release];
}

#pragma mark -
#pragma mark Table view data source
- (NSInteger)tableView:(UITableView *)tableView 
sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index
{
    int i = 0;
    for(NSArray *array in detailListArray)
    {
        NSString *string = [array objectAtIndex:0];
        if([string compare:title] == NSOrderedSame)
            break;
        i++;
    }
    return i;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return detailListArray.count;
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    NSArray *array = [detailListArray objectAtIndex:section];
    return [array objectAtIndex:0];
}

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView 
{
    NSMutableArray *titleArray = [NSMutableArray array];
    [titleArray addObject:@"A"];
    [titleArray addObject:@"B"];
    [titleArray addObject:@"C"];
    [titleArray addObject:@"D"];
    [titleArray addObject:@"E"];
    [titleArray addObject:@"F"];
    [titleArray addObject:@"G"];
    [titleArray addObject:@"H"];
    [titleArray addObject:@"I"];
    [titleArray addObject:@"J"];
    [titleArray addObject:@"K"];
    [titleArray addObject:@"L"];
    [titleArray addObject:@"M"];
    [titleArray addObject:@"N"];
    [titleArray addObject:@"O"];
    [titleArray addObject:@"P"];
    [titleArray addObject:@"Q"];
    [titleArray addObject:@"R"];
    [titleArray addObject:@"S"];
    [titleArray addObject:@"T"];
    [titleArray addObject:@"U"];
    [titleArray addObject:@"V"];
    [titleArray addObject:@"W"];
    [titleArray addObject:@"X"];
    [titleArray addObject:@"Y"];
    [titleArray addObject:@"Z"];
    return titleArray;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    NSArray *array = [detailListArray objectAtIndex:section];
    return (array.count - 1);
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
                                                    reuseIdentifier:@"CELL"] autorelease];
    NSArray *array = [detailListArray objectAtIndex:indexPath.section];
    NSDictionary *dict = [array objectAtIndex:indexPath.row + 1];
    cell.textLabel.text = [dict objectForKey:@"Name"];
    return cell;
}

#pragma mark -
#pragma mark Table view delegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSArray *array = [detailListArray objectAtIndex:indexPath.section];
    NSDictionary *dict = [array objectAtIndex:indexPath.row + 1];
    int entryID = [[dict objectForKey:@"ID"] intValue];
     // Do what ever you want to do with the selected row here....
}

This is the code that I have used in one of the recent projects.