Question

I would like to ask how could I count object type inside array. For example

this is my dataclass

+ (id)LocationWithID:(NSString *)UniqueID name:(NSString *)name address:(NSString *)address latitude:(float )latitude longitude:(float )longitude locationtype:(NSString *)locationtype country:(NSString *)country distance:(float )distance;

and this is my array

[array addObject:[dataclass LocationWithID:UniqueID name:name address:address latitude:latitude longitude:longitude locationtype:locationtype country:country distance:distance]];

and i would like to count how many country in this object. Normally we use
[array count];
but this will count all the object in the array. Now in my case i want to count non-repeated object for example i got an array contain 3 United kingdom, 5 USA, 7 Japan, 3 China and the result i want is country type = 4.

I would like to create several section for Table View according to the country type. Anyone?

Answer 1

You can use a dictionary to put objects with the same country in a separate array:

NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];
for (dataclass *location in array) {
    if (![dictionary objectForKey:location.country]) {
        [dictionary setObject:[NSMutableArray array] forKey:location.country];
    }
    [(NSMutableArray *)[dictionary objectForKey:location.country] addObject:location];
}

Now, not only you can get the number of different countries like this:

int countriesCount = [dictionary count];

But also, it is easy to populate each section of your table view with locations from the corresponding country.

You can retrieve all the locations for a specific country that has the name countryName, like this:

NSArray *locationsForCountry = [dictionary objectForKey:countryName];

You can also have the list of all the countries like this:

NSArray *countries = [[dictionary keyEnumerator] allObjects];