How to Mirror an NSMutableArray?

Question

How does one mirror an NSMutableArray (first element becomes last one, second becomes second to last, ...)?

score 4 · Answer 1 · edited Jan 28 '13 at 12:16

4

NSArray* reversedArray = [[orgArray reverseObjectEnumerator] allObjects];

edited Jan 28 '13 at 12:16

mrueg

answered Jan 28 '13 at 11:54

Parag Bafna

This will not change your original array, however, i.e the mirroring won't be in-place. – mrueg Jan 28 '13 at 12:17

score 3 · Accepted Answer · edited Jan 29 '13 at 18:34

3

Use -[NSMutableArray exchangeObjectAtIndex:withObjectAtIndex:].

So, if your array is called a:

NSUInteger c = [a count];
for(NSUInteger i = 0; i < (c / 2); ++i) {
    [a exchangeObjectAtIndex:i withObjectAtIndex:(c - i) - 1];
}

edited Jan 29 '13 at 18:34

Peter Hosey

answered Jan 28 '13 at 11:51

mrueg

1

+1, As you mirrored the array itself. – Anoop Vaidya Jan 28 '13 at 13:26
1

There's a small error btw : it should be `c - i - 1` since `c - 0` is out of bounds. – Fatso Jan 28 '13 at 14:25

2 Answers2