Grouping NSArray of NSDictionary based on a key in NSDictionay - ios

Question

I am trying to filter out a NSArray of NSDictionaries. With my below example, I want dict1, dict2 & dict4 grouped in one array, dict3 & dict5 grouped in second array and dict6 in third array.
I am getting this data in NSArray, so essentially the "orig" array below is my input and I know that I need to do grouping based on "Name" key.
Instead of looping through the NSArray I though of using valueForKeyPath to return me array based on the key path but this does not work (crashes with logs -[NSMutableArray addObjectsFromArray:]: array argument is not an NSArray').
Any suggestion.
NSDictionary *dict1 = #{#"Name" : #"T1", #"Age" : #"25"};
NSDictionary *dict2 = #{#"Name" : #"T1", #"Age" : #"25"};
NSDictionary *dict3 = #{#"Name" : #"T2", #"Age" : #"27"};
NSDictionary *dict4 = #{#"Name" : #"T1", #"Age" : #"25"};
NSDictionary *dict5 = #{#"Name" : #"T2", #"Age" : #"27"};
NSDictionary *dict6 = #{#"Name" : #"T3", #"Age" : #"28"};
NSArray *orig = #[dict1, dict2, dict3, dict4, dict5, dict6];
NSMutableArray *final = [NSMutableArray array];
final = [orig valueForKeyPath:#"#unionOfArrays.Name"];
NSLog(#"Final = %#", final);

Answer 1

It's a little hard to tell if what you want is three different arrays where each one only contains entries with a specific Name value (as your first paragraph suggests) or if you want a single array where the entries are sorted by Name (as your second paragraph suggests). Regardless,
To sort orig by the value of the Name field:
NSArray *sortedByName = [orig sortedArrayUsingDescriptors:#[[NSSortDescriptor sortDescriptorWithKey:#"Name" ascending:YES]]];
To get a new array by selecting only entries with a specific value for Name:
NSArray *t1Only = [orig filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"Name = %#", #"T1"]];

Answer 2

If the desired output is an array of arrays, you can get there by building a dictionary keyed by the name attribute in the orig dictionaries:
- (NSArray *)collateByName:(NSArray *)original {
NSMutableDictionary *collate = [NSMutableDictionary dictionary];
for (NSDictionary *d in original) {
NSString *newKey = d[#"Name"];
NSMutableArray *newValue = collate[newKey];
if (!newValue) {
newValue = [NSMutableArray array];
collate[newKey] = newValue;
}
[newValue addObject:d];
}
return [collate allValues];
}
It's a little verbose, but clear, I think. If you want to decide the attribute to distinguish with programmatically, pass in another param called attribute and replace the literal #"Name" with it.