Convenience macro for creating singletons and the like. Handy if you define a lot of fixture objects.

gistfile1.m

#define SHARED_INSTANCE(EXPR) \
    ^(){ \
        static typeof((EXPR)) instance; \
        static dispatch_once_t onceToken; \
        dispatch_once(&onceToken, ^{ \
            instance = EXPR;\
        });\
        return instance;\
    }()

Use it like so

@implementation XYFixtures

+ (XYUser *)steve
{
    return SHARED_INSTANCE([[XYUser alloc] initWithName:@"Steve"]);
}

@end