Grouping of Custom Objects in Objective-C

Question

I have and array of custom objects of Person Class

Person : NSObject{
    NSString *firstName;
    NSString *lastName; 
    NSString *age;
}

NSMutableArray          


        

Answer 1

I have created a small library called Linq-to-ObjectiveC which provides a number of methods which make is easier to query arrays. In order to perform the group operation you require you can simply do the following:

NSDictionary* groupedByName = [personsArray groupBy:^id(id person) {
   return [person firstName];
}];

This would return a dictionary where the keys are the distinct first names, and each value is an array of 'person' objects that have the given first name.