Group element in NSMutableArray which contains object

Question

I have an NSMutableArray that contains an object of a class model in each position like this. The class model contains 2 types of information, which we will call id and name . So, in every location of my NSMutableArray I have an object that contains 2 information.

Then, in the first position of my NSMutableArray I have

{
 id = 1;
 name = "Dan"; //this is the first object in NSMutableArray
}

In the second position of NSMutableArray, I have:

{
 id = 1;
 name = "Luca"; 
}

In the third position

{
 id = 2;
 name = "Tom"; 
}

and so on..

Ok, my goal is to make the union of identical IDs between the various objects within the SNMutableArray but it's too difficult!

For example, if I have:

{
 id = 1;
 name = "Tom"; 
}

{
 id = 1;
 name = "Luca"; 
}

{
 id = 2;
 name = "Steve"; 
}

{
 id = 2;
 name = "Jhon"; 
}

{
 id = 3;
 name = "Andrew"; 
}

The goal is:

{
 id = 1;
 name = "Tom"; 
 name = "Luca"; 
}
{
 id = 2;
 name = "Steve";
 name = "Jhon"; 

}
{
 id = 3;
 name = "Andrew"; 
}

Any ideas? would like to use this in the cellForRowAtIndexPath method and I tried to write this: (cm is my class model and myArray is the NSMutableArray which contains an object of cm class)

ClassModel *cm = [myArray objectAtIndex:indexPath.row];


NSMutableArray * resultArray = [NSMutableArray new];
NSArray * groups = [array valueForKeyPath:cm.ID];
for (NSString * groupId in groups)
{
     NSMutableDictionary * entry = [NSMutableDictionary new];
     [insert setObject: groupId forKey: @ "groupId"];

     NSArray * groupNames = [array filteredArrayUsingPredicate: [NSPredicate predicateWithFormat: @ "groupId =% @", groupId]];
     for (int i = 0; i <groupNames.count; i ++)
     {
         NSString * name = [[groupNames objectAtIndex: i] objectForKey: @ "name"];
         [entry setObject: name forKey: [NSS string stringWithFormat: @ "name% d", i + 1]];
     }
     [resultArray addObject: entry];
}

NSLog (@ "% @", resultArray);

But this does not work..maybe because each element in my array is an object?? .. Help!

Answer 1

You have the right basic idea, but you shouldn't try and do this in cellForRowAt . Rather, you need to create a new array that has the data in the required structure and use that array as the source for your tableview. You will also need to create a new class to put in the array; one that has an id and an NSMutableArray for the names (I won't show this but I will call it GroupClassModel )

Use something like:

NSMutableDictionary *groups = [NSMutableDictionary new]
for (ClassModel *cm in array) {
    GroupClassModel *gcm = groups[cm.id];
    if (gcm == nil) {
        gcm = [GroupClassModel new];
        gcm.id = cm.id
        groups[cm.id] = gcm
    }
    [gcm.names addObject:cm.name];
}

NSArray *groupedName = [groups allValues];
// Finally, sort groupedName by id if that is required.