+ (id)sharedInstance{
static id sharedInstance; static dispatch_once_t once; dispatch_once(&once, ^{ sharedInstance = [[[self class] alloc] init]; }); return sharedInstance;}本文共 228 字，大约阅读时间需要 1 分钟。
+ (id)sharedInstance{
static id sharedInstance; static dispatch_once_t once; dispatch_once(&once, ^{ sharedInstance = [[[self class] alloc] init]; }); return sharedInstance;}转载于:https://www.cnblogs.com/liuxingzi/p/3600537.html