iOS实现代码只执行一次

- (void)viewDidLoad {  [super viewDidLoad];  // Do any additional setup after loading the view, typically from a nib.   [self performSelector:@selector(wangmumu:) withObject:@"100" afterDelay:1];} - (void) wangmumu:(NSString *)han{  static dispatch_once_t hanwanjie;//只执行一次  dispatch_once(&hanwanjie, ^{    NSLog(@"12345678910");  });     int niha = [han intValue] - 1;  if (niha == 10) {    return;  }  [self performSelector:@selector(hanwanjie:) withObject:[NSString stringWithFormat:@"%d",niha] afterDelay:1];}