memo

    dispatch_after
            StrongSelf(self)
            __weak typeof(self) wkSelf = self;
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                __strong typeof(self) stSelf = wkSelf;
                //todo: something
                }
            });