单例 2014/12/31 32960 清华大佬耗费三个月吐血整理的几百G的资源,免费分享!....>>> + (instancetype)sharedInstance { static id sharedInstance = nil; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ sharedInstance = [[self alloc] init]; }); return sharedInstance; }