May I use NSCoder::encodeInteger:forKey: and decodeIntegerForKey: methods with argument of type NSUInteger?

Question

I need to encode and decode property of type NSUInteger with NSCoder.

Is it safe to use NSCoder::encodeInteger:forKey: and NSCoder::decodeIntegerForKey: methods for that?

The other way around that comes to my mind is to wrap the unsigned integer into NSNumber first. But that means some more code and I do not like it much.

score 5 · Answer 1 · edited Aug 24 '13 at 18:12

5

Is it safe to use NSCoder::encodeInteger:forKey: and NSCoder::decodeIntegerForKey: methods for that?

Yes, it is safe, because all architectures on OS X and iOS use the two's complement for representing signed numbers. For example (assuming a 32-bit architecture), in

NSUInteger n = 0xFFFFFFFF;
[aCoder encodeInteger:n forKey:@"n"];

n is converted to a signed integer with the same memory representation, which is -1.

And in

 NSUInteger n = [aDecoder decodeIntegerForKey:@"n"];

the signed integer -1 is converted back to an unsigned integer with the same memory representation, so that you get back the original value.

edited Aug 24 '13 at 18:12

iHunter

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answered Aug 17 '13 at 21:26

Martin R

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Does this answer hold true for 64-bit architecture? – rmtheis Apr 11 '15 at 17:54
@rmtheis: Yes, I am pretty sure it does (NSUInteger is a 64-bit integer on 64-bit architectures. I just gave an example for 32-bit). – Martin R Apr 11 '15 at 17:58

May I use NSCoder::encodeInteger:forKey: and decodeIntegerForKey: methods with argument of type NSUInteger?

1 Answers1