Random Objective-C Question

I've only just started on Obj-C but I got the impression that the initial declaration has to be something like:

NSAttributedString *attribString = [NSAttributedString alloc];

So if you're not initially pointing the declaration at a new object instance can you not go...

NSAttributedString *attribString = Nil;

...to make sure that it returns Null until you allocate a new instance to it?