objective-c-nullability

This is a question on how to gracefully circumvent the nullability of init in NSObject class. So here is a classic objective-c implementation: + (instancetype)sharedInstance { static dispatch_once_t onceToken; static id sharedInstance; dispatch_once(&onceToken, ^ { sharedInstance = [[self alloc] init]; }); return sharedInstance; } But now I want to declare it as nonnull , if possible: + (nonnull instancetype)sharedInstance; Unfortunately, init returns a nullable instancetype value. Should I add an NSAssert or something after calling init ? I noticed that some people even document nonnull

In Xcode 7 GM I started to get this warning: Pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) In the following function declaration (NSUserDefaults extension) - (void)setObject:(nullable id)value forKey:(NSString *)defaultName objectChanged:(void(^)(NSUserDefaults *userDefaults, id value))changeHandler objectRamains:(void(^)(NSUserDefaults *userDefaults, id value))remainHandler; Why this warning is showing and how should I fix it? You need to specify nullable also for the handlers/blocks - (void)setObject:(nullable id)value forKey:(nonnull NSString *

With Xcode 6.3 there were new annotations introduced for better expressing the intention of API's in Objective-C (and to ensure better Swift support of course). Those annotations were of course nonnull , nullable and null_unspecified . But with Xcode 7, there is a lot of warnings appearing such as: Pointer is missing a nullability type specifier (_Nonnull, _Nullable or _Null_unspecified). In addition to that, Apple uses another type of nullability specifiers, marking their C code ( source ): CFArrayRef __nonnull CFArrayCreate(
CFAllocatorRef __nullable allocator, const void * __nonnull * _

I've been learning Swift lately. I decided to write a hybrid Swift/Objective-C app that did compute-intensive tasks using the same algorithm implemented in both languages. The program calculates a large array of prime numbers. I defined a protocol that both the Swift and the Objective-C version of the calculate object are supposed to conform to. The objects are both singletons, so I created a typical singleton access method in Objective-C: + (NSObject <CalcPrimesProtocol> *) sharedInstance; The whole protocol looks like this: #import <Foundation/Foundation.h> @class ComputeRecord; typedef void