CODEWITHSUNDEEP
objective-cnsstring
Khoi
Khoi

Reputation: 21

Seems like null NSString has length 6?

I have a person object of class Person with property is address, age. When I check properties, I print address on screen with:

      NSLog(@"Add: %@, length: %i", person.address, [person.address length]);

The result is: Add: nil, length: 6

Can you explain for me why the string is null but its length shows as 6?

Thanks.

Upvotes: 2

Views: 210

Answers (3)

Glen
Glen

Reputation: 11

You are probably getting the string value of "(null)" in the field somehow, which is 6 characters long.

Upvotes: 1

Stephen Darlington
Stephen Darlington

Reputation: 52565

The answer you're probably looking for is: you're using the wrong string format specifier. I'm not sure what %i is; %d is for integers and %u for unsigned, so you need:

NSLog(@"Add: %@, lenght: %u", person.address, [person.address length]);

But... the length is possibly not returning what you think it is.

If person.address is nil, then sending the message length to it won't return the length (what is the length of "nothing"?). As it happens, the Objective C runtime will return zero so your example "works" but is arguably not correct.

Upvotes: 0

Mario
Mario

Reputation: 4520

What type is address? NSString I assume? use %d or %lu for length (and cast to unsigned long if using %lu) instead of %i - that should give correct result.

Length gives a NSUInteger as a result, correct string format specifier would hence be %lu although %d should also work (thinking of it, I always use %d). I never as %i...

NSLog(@"%lu", (unsigned long)string.length)

Look at the format specifies:

https://developer.apple.com/library/mac/ipad/#documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html

Upvotes: 0

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