How to access NSMutableArray given an object in it

Question

If I am given an object that I know is in an NSMutableArray, how can I access that NSMutableArray and the index of the object in that NSMutableArray?

Answer 1

Not directly. You would, at least, need references to all possible arrays the object might be in. With that, you could ask each for objectAtIndex:. If the return value is not NSNotFound, the object is in the array.

Of course, that is potentially slow and a sign of bad design.

One solution would be to have a reference from your object to the array. This will work, but you need to makes sure the circular reference doesn't cause a leak.

Answer 2

You can use the function indexOfObject:(id)object on the array and pass your object as the argument to receive the index.

For instance, let your array be NSMutableArray *array and the object be id obj. Then, int index = [array indexObObject:obj];