iOS - Count and return number of duplicates in array

Question

I am developing a Business directory where I have an array containing business types (Hairdresser, mechanic, etc) and an array containing business sections as letters (Eg. A or B or C or D... or Z, etc).

The data will be shown in a tableview with an A-Z index.

I have set it up as follows but can't think of a way to return the section numbers based on the business section letter.

I want to return the number of objects in the array that have the same business type letter (Eg. A or B or C or D... or Z, etc) in each section.

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 26;
}

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView {

    NSMutableArray *tempArray = [[NSMutableArray alloc] init];
    [tempArray addObject:@"A"];
    [tempArray addObject:@"B"];
    [tempArray addObject:@"C"];
    [tempArray addObject:@"D"];
    [tempArray addObject:@"E"];
    [tempArray addObject:@"F"];
    [tempArray addObject:@"G"];
    [tempArray addObject:@"H"];
    [tempArray addObject:@"I"];
    [tempArray addObject:@"J"];
    [tempArray addObject:@"K"];
    [tempArray addObject:@"L"];
    [tempArray addObject:@"M"];
    [tempArray addObject:@"N"];
    [tempArray addObject:@"O"];
    [tempArray addObject:@"P"];
    [tempArray addObject:@"Q"];
    [tempArray addObject:@"R"];
    [tempArray addObject:@"S"];
    [tempArray addObject:@"T"];
    [tempArray addObject:@"U"];
    [tempArray addObject:@"V"];
    [tempArray addObject:@"W"];
    [tempArray addObject:@"X"];
    [tempArray addObject:@"Y"];
    [tempArray addObject:@"Z"];

    return tempArray;

}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// I want to return the number of objects in the array that have the same section name (EG. A or B or C etc)
}

Anoop Vaidya · Accepted Answer · 2013-01-07 10:27:39Z

You can create a Dictionary or an Array of array. Either one will work for you.

Just see this example :

I have two arrays alphabets which contains A, B, C...Z. And other array is words which contains at index[0]={apple, axe..}, index[1]={ball, bat}, index[3]={cow, cat, car, cardamom}.... So forming a two-Dimentional array.

NOTE: Few unwanted things are here, you can ommit them, like subtitle.

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{
    return [self.words count];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
    return [[self.words objectAtIndex:section]count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{

    UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier:@"cell"];
    if (cell==nil) {
        cell=[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:@"cell"];
    }
    cell.textLabel.text=[[self.words objectAtIndex:indexPath.section]objectAtIndex:indexPath.row];
    cell.detailTextLabel.text=[NSString stringWithFormat:@"This is detailed subtitle for %@.",cell.textLabel.text];
    return cell;

}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section{
    return [self.alphabets objectAtIndex:section];
}

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView;{
    return self.alphabets;
}

David Rönnqvist · Accepted Answer · 2013-01-07 10:25:16Z

0

You can create a NSCountedSet from the original array that knows how many times each object occures

NSCountedSet *countedSet = [[NSCountedSet alloc] initWithArray:yourArray];

Then you can get the count for each object using countForObject: on the set.

If the order matters to you then you can enumerate over the array and call countForObject: on the set with the object from the array.

answered Jan 7, 2013 at 10:25

David Rönnqvist

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