轮换电话号码中间4位为-号

- (void)viewDidLoad{    [super viewDidLoad];    // Do any additional setup after loading the view.        //电话号码    UILabel *telLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 100, 200, 20)];    telLabel.textColor = [UIColor grayColor];    telLabel.text = @"13793333281";    //字符串的截取    NSString *string = [telLabel.text substringWithRange:NSMakeRange(4,4)];    //字符串的替换    telLabel.text = [telLabel.text stringByReplacingOccurrencesOfString:string withString:@"----"];    [self.view addSubview:telLabel];}