How do I add data into NSMutableArray by manually assigning index?

Question

Is there any way to manually control which index we want to add our data to with an NSMutableArray? In PHP, for example, we can do:

$foo[2] = "fafa";
$foo[8] = "haha";

Can the manual assigning of indexing be done on NSMutableArray?

Answer 1

NSMutableArrays are not sparse -- they cannot have gaps where no objects are stored. It is possible to insert an object at any index from 0 to length - 1, using insertObject:atIndex: (as Edu mentioned), but other than that you can only append objects (using addObject:).

If you need to associate objects with arbitrary integers, you can use an NSMapTable -- the functional interface allows integer keys, or simply use an NSMutableDictionary, with NSNumber keys (as drewag suggested).

See also: How to do sparse array in Cocoa

Answer 2

Just because it's not entirely clear to me that TeamStar wants a sparse array, I'll just mention that you can assign objects to specific indexes within an NSMutableArray – so long as the array is already long enough – using -replaceObjectAtIndex:withObject: and the other -replace… methods.