iOS中单例的两种方法

1.单例第一种方法

static Manager *manager = nil;

+ (Manager *) shareManagerInit {

if (!manager) {

  manager = [[Manager alloc] init];

   }

  return manager;

}

2.单例第二种方法

static Employee *emp = nil;

+ (Employee *) shareManagerInit {

if (!emp) {

  static dispatch_once_t onceToken;

  dispatch_once(&onceToken , ^{

  emp = [[Employee alloc] init];

 

});

  return emp;

  }

}