Better Singleton in iOS

//  Created by ziggear on 13-5-26
//  fw & courtesy: http://cocoasamurai.blogspot.com/2011/04/singletons-your-doing-them-wrong.html
//  usage: 
//  @implementation SomeClass
//      ....
//      kSingletonSynthesize(SomeClass)
//  @end

//Thread-safe block
#define kRunInSecurutyBlock(lines) static dispatch_once_t pred; dispatch_once(&pred, ^{ \
lines \
});

//Singleton
#define kSingletonSynthesize(Class) + (id)sharedMan { \
    static id sharedManager = nil;\
    if (self == [Class class]) { \
       kRunInSecurutyBlock(sharedManager = [[Class alloc] init];) \
    } \
    return sharedManager; \
}