objective c - NSUInteger should not be used in format strings?

Question

Here's my code in all it's glory:

[NSString stringWithFormat:@"Total Properties: %d", (int)[inArray count]];

Which gets me an Xcode 5.1 warning:

Values of type 'NSUInteger' should not be used as format arguments; add an explicit cast to 'unsigned long' instead

Ok so I'm confused. The value really is a 32-bit int, and I cast it to a 32-bit int. So what is this NSUInteger it's complaining about (the count I assume) and why doesn't this cast fix it?

Answer 1

NSUInteger and NSInteger are different lengths on 32-bit (int) and 64-bit (long). In order for one format specifier to work for both architectures, you must use a long specifier and cast the value to long:

Type    Format Specifier    Cast
----    ----------------    ----
NSInteger    %ld            long
NSUInteger   %lu            unsigned long

So, for example, your code becomes:

[NSString stringWithFormat:@"Total Properties: %lu", (unsigned long)[inArray count]];

There is very little work to do, really, because Xcode's Fix-It feature will do this for you automatically.