Sort NSMutableArray with custom objects by another NSMutableArray

Question

I have 2 NSMutableArrays. First array contains custom object intances with property NSString *itemID, second array contains only from NSString objects with same values of itemID, but in another order. I need to sort first array by itemID property of each object, and it should be sorted like second array.

How I can do this?

http://stackoverflow.com/questions/805547/how-to-sort-an-nsmutablearray-with-custom-objects-in-it/805589#805589 — Nag_iphone, Apr 11 '13 at 09:00
I've seen this solution, and it's not suitable for my question — Timur Mustafaev, Apr 11 '13 at 09:18

βhargavḯ · Accepted Answer · 2013-04-11T09:04:13.300

3

guideArray = < YOUR SECOND ARRAY WITH STRING OBJECT >;    
unsortedArray = < YOUR FIRST ARRAY WITH CUSTOM OBJECT >;

[unsortedArray sortUsingComparator:^(id o1, id o2) {
    Items *item1 = o1;
    Items *item2 = o2;
    NSInteger idx1 = [guideArray indexOfObject:item1.ItemID];
    NSInteger idx2 = [guideArray indexOfObject:item2.ItemID];
    return idx1 - idx2;
}];
NSLog(@"%@",unsortedArray);

edited Apr 11 '13 at 09:04

answered Apr 11 '13 at 08:48

βhargavḯ

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Jonathan Cichon · Answer 2 · 2013-04-11T08:49:23.723

Store the custom objects in an dictionary with itemID as key, use this dictionary as lookup to sort the objects:

    NSArray *objects; // your objects
    NSMutableArray *hintArray; // your sorted IDs
    NSMutableDictionary *lookupDict = [[NSMutableDictionary alloc] initWithCapacity:[objects count]];
    NSMutableArray *sortedObjects = [[NSMutableArray alloc] initWithCapacity:[hintArray count]];

    for (id object in objects) {
        [lookupDict setValue:object forKey:[object itemID]];
    }

    for (id hint in hintArray) {
        [sortedObjects addObject:[lookupDict valueForKey:hint]];
    }

EDIT: Solution with inplace sort of objects:

    NSMutableArray *objects;
    NSMutableArray *hintArray;
    NSMutableDictionary *lookupDict = [[NSMutableDictionary alloc] initWithCapacity:[hintArray count]];

    int i = 0;
    for (NSString *itemID in hintArray) {
        [lookupDict setValue:[NSNumber numberWithInt:i] forKey:itemID];
        i++;
    }

    [objects sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        return [[lookupDict valueForKey:[obj1 itemID]] compare:[lookupDict valueForKey:[obj2 itemID]]];
    }];

NSDictionary adds not to end of the list. So it wouldn't help — Timur Mustafaev, Apr 11 '13 at 08:47
I dont get your comment. I simple build lookup dictionaries to avoid searching for each item in the sorted id-list, which will become very expensive when you got a large amount of items. — Jonathan Cichon, Apr 11 '13 at 08:51

Niru Mukund Shah · Answer 3 · 2013-04-11T08:55:46.897

1

You can compare your two objects using following syntax :-

[items sortUsingComparator:^NSComparisonResult(Attribute *obj1, Attribute *obj2) 
{
    return [[NSNumber numberWithInt:[stringOrder indexOfObject:obj1.itemID]] compare:[NSNumber numberWithInt:[stringOrder indexOfObject:obj2.itemID]]]
}];

or else you can use following snippet :

NSArray* sortedKeys = [dict keysSortedByValueUsingComparator:^(id obj1, id obj2)
 {
    return [obj1 compareTo:obj2];
 }

Enjoy Programming !

edited Apr 11 '13 at 08:55

answered Apr 11 '13 at 08:42

Niru Mukund Shah

4,637
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1

Thanks, this is also working answer – Timur Mustafaev Apr 11 '13 at 08:57

Sort NSMutableArray with custom objects by another NSMutableArray

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