What is reason of Warning "Pointer is missing a nullability type specifier"?

Question

+ (UIColor*) getColorWithHexa(NSString*)hexString;

:

This is a method definition in my class. It's causing a warning. What is cause of similar warnings and how can these be resolved?

I am returning an UIColor object, while that question relates to blocks, which is given in comments.

So, it's helpful.

Don't post microscopic screenshots. Post code! Copy & paste is pretty easy. — vadian
– vadian, Commented Feb 24, 2016 at 11:28
@vadian both Questions are totally different. This questions relates to What is reason, its not a solution, or anything mentioned in your link. Here its a method, while that is complete separate block. — Chatar Veer Suthar
– Chatar Veer Suthar, Commented Feb 24, 2016 at 11:39
e.g. + (UIColor * _Nullable) getColorWithHexa(NSString * _Nonnull)hexString;, but you can fit your class's entire interface between the NS_ASSUME_NONNULL_BEGIN and NS_ASSUME_NONNULL_END directives as well, which defines _Nonnull for every object automatically. — holex
– holex, Commented Feb 24, 2016 at 12:16

Cœur · Accepted Answer · 2018-08-20 09:53:36Z

16

NS_ASSUME_NONNULL_BEGIN/END:

Annotating any pointer in an Objective-C header file causes the compiler to expect annotations for the entire file, bringing on a cascade of warnings. Given that most annotations will be nonnull, a new macro can help streamline the process of annotating existing classes. Simply mark the beginning and end of a section of your header with NS_ASSUME_NONNULL_BEGIN and ..._END, then mark the exceptions.

So,you have simply do.

NS_ASSUME_NONNULL_BEGIN
+ (UIColor*) getColorWithHexaCode:(NSString*)hexString;
NS_ASSUME_NONNULL_END

This is defined in

"NSObjCRuntime.h"

#define NS_ASSUME_NONNULL_BEGIN _Pragma("clang assume_nonnull begin")
#define NS_ASSUME_NONNULL_END _Pragma("clang assume_nonnull end")

edited Aug 20, 2018 at 9:53

Cœur

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answered Feb 24, 2016 at 11:45

Chatar Veer Suthar

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1 Comment

Elise van Looij Over a year ago

NS_ASSUME_NONNULL_BEGIN / END is really simple, until you specify a single non null parameter and then you'll be hounded by 'missing nullability type specifier' warnings for the rest of your life. Quite possibly beyond that.

Cœur · Accepted Answer · 2016-02-24 12:12:00Z

9

You got this warning when somewhere in the file you used either _Nonnull, _Nullable, _Null_unspecified, __nullable, __nonnull, nullable or nonnull. Could also happen if the specifier was added through a macro.

To fix the warning:

you can remove all occurrences of nullability (not recommended)
you can assume all parameters and returned values are _Nonnull using NS_ASSUME_NONNULL_BEGIN and NS_ASSUME_NONNULL_END (recommended)

answered Feb 24, 2016 at 12:12

Cœur

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2 Comments

bcmills Over a year ago

As far as I can tell this description is correct, but do you have a source with more detail on the intended semantics? The Clang documentation at clang.llvm.org/docs/… describes the diagnostic text but not its actual meaning.

bcmills Over a year ago

The only definitive reference I have so far is the Clang implementation itself: github.com/llvm/llvm-project/blob/…

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