How to assign an empty NSData value and not a NULL value?

Question

How to assign null value to NSData and not NULL?

I did not want to assign zero or nil. I wanted an empty value, not like the code below.

NSData* variable = NULL; // not even assigning to nil NSData* variable = nil; 

Answer 1

 NSData *variable = [[NSData alloc] init]; // don't forget to release if not using ARC. 

Answer 2

 NSData *data = [[NSData alloc] init];