Question

Is it possible to set a tag for an NSMutableArray? I have to somehow determine, in an array of arrays, the single array which needs to be rewritten, and if I could just set the tag to that inner array to 1 (or some other number), this would be extremely easy.

Example:

NSMutableArray* outerArray = [NSMutableArray new];

NSMutableArray* innerArray1 = [NSMutableArray new];
NSMutableArray* innerArray2 = [NSMutableArray new];
NSMutableArray* innerArray3 = [NSMutableArray new];
NSMutableArray* innerArray4 = [NSMutableArray new];

[outerArray addObject:innerArray1];
[outerArray addObject:innerArray2];
[outerArray addObject:innerArray3];
[outerArray addObject:innerArray4];

//now let's say innerArray1 needs to be rewritten
//I would like to be able to do this

[innerArray1 setTag:100];

//then later, when I need to determine which of the arrays inside outerArray
//needs to be rewritten, I can just do this

for(NSMutableArray* temp in outerArray) {
    if(temp.tag == 100) {
        //do what I need to do
    }
}

But you can’t use setTag: with NSMutableArrays. What would be a workaround?

Answer 1

Arrays are ordered collections, so why don’t you just keep track of which index needs to be rewritten.

When something happens such that the array at index 0 (which, in your example, would be innerArray1) of outer array needs to be written, cache index 0 — as a property if this routine needs to span across separate methods.

Then, when it comes time to do the rewrite, consult the cached index. Retrieve the array to be rewritten like this: NSArray *arrayToRewrite = [outerArray objectAtIndex:cachedIndexToRewrite]; Or access it directly: [[outerArray objectAtIndex:cachedIndexToRewrite] replaceObjectAtIndex:whatever withObject:whatever];