嗯，就是内存方面的

UIScrollView* scroll = [[UIScrollView alloc] init];        NSLog(@"scroll retain count 1 is %d", [scroll retainCount]);        ControlPanel* cp = [[ControlPanel alloc] init];        NSLog(@"control panel retain count 1 is %d", [cp retainCount]);        [scroll addSubview:cp];        NSLog(@"control panel retain count 2 is %d", [cp retainCount]);        NSLog(@"scroll retain count 2 is %d", [scroll retainCount]);        [scroll release];    NSLog(@"control panel retain count 3 is %d", [cp retainCount]);    NSLog(@"scroll retain count 3 is %d", [scroll retainCount]);        [cp release];    return NO;

2011-08-18 09:57:25.352 wolaidianDemo[3280:607] scroll retain count 1 is 1
2011-08-18 09:57:33.784 wolaidianDemo[3280:607] control panel retain count 1 is 1
2011-08-18 09:57:38.320 wolaidianDemo[3280:607] control panel retain count 2 is 2
2011-08-18 09:57:41.218 wolaidianDemo[3280:607] scroll retain count 2 is 1
2011-08-18 09:57:44.414 wolaidianDemo[3280:607] control panel retain count 3 is 1