Using integer indices into arrays of objects (instead of iterators, or pointers to the objects themselves) has saved my ass many times.
Say you have a vector<Object>. Well, you wouldn’t store pointers of type Object* to an element of this array, ever, because if the vector gets resized, all objects get deallocated/reallocated and so all your previous references will be invalid. But if you store a vector<Object*> and save an external reference to an Object* within that vector, then that’s no problem.
But anyway, storing integer arrays is much better than storing copies of pointers. For one, if the pointer gets deleted, you’re not left with an invalid / dangling pointer somewhere. Checking if a reference into the array is valid because you just have to check the integer index is between 0 and (.size()-1).