Question

What would be equivalent Objective C for this:

template<class T>
class Singleton 
{ 
public: 
    static T * instance() 
    { 
        static T t; 
        return &t; 
    }
private: 
    Singleton(); 
    ~Singleton(); 
};

---

While calling:

friend class Singletone<MyManagerClass>;

Answer 1

#define SINGLETON_FOR_CLASS(classname)                          \
                                                                \
static classname *shared##classname = nil;                      \
                                                                \
+ (classname *)instance {                                       \
    @synchronized(self) {                                       \
        if (shared##classname == nil) {                         \
            [[self alloc] init];                                \
        }                                                       \
    }                                                           \
                                                                \
    return shared##classname;                                   \
}                                                               \
                                                                \
+ (id)allocWithZone:(NSZone *)zone {                            \
                                                                \
    @synchronized(self) {                                       \
        if (shared##classname == nil) {                         \
            shared##classname = [super allocWithZone:zone];     \
            return shared##classname;                           \
        }                                                       \
    }                                                           \
                                                                \
    return nil;                                                 \
}                                                               \
                                                                \
- (id)copyWithZone:(NSZone *)zone {                             \
                                                                \
    return self;                                                \
}                                                               \
                                                                \
- (id)retain {                                                  \
                                                                \
    return self;                                                \
}                                                               \
                                                                \
- (NSUInteger)retainCount {                                     \
                                                                \
    return UINT_MAX;                                            \
}                                                               \
                                                                \
- (void)release {                                               \
                                                                \
}                                                               \
                                                                \
- (id)autorelease {                                             \
                                                                \
    return self;                                                \
}                                                               \