Group element in NSMutableArray which contains object - ios

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.