看了网上的，很多都是监听键盘删除，那样的方法很不好，而且太麻烦
看看我设置的，直接是3-4-4格式的展示和删除的使用，这几行代码就可以

pragma mark -- PhoneFormat

• (BOOL)PhoneFormatTextField:(UITextField *)textField string:(NSString *)string rang:(NSRange)range
  {
  NSString textt = textField.text;
  textt = [textt stringByReplacingCharactersInRange:range withString:string];
  NSMutableString texttitle=[[NSMutableString alloc]initWithString:textt];

  if ([self.accountTextfield.text length] <= texttitle.length) // 判断删除操作
  {
  if (texttitle.length == 4) {
  [texttitle insertString:@"-"atIndex:3];
  }else if (texttitle.length == 9){
  [texttitle insertString:@"-"atIndex:8];
  }

    if (texttitle.length == 13) {
        [self.loginButton setImage:[UIImage imageNamed:@"确定可操作button"] forState:UIControlStateNormal];
        self.loginButton.userInteractionEnabled = YES;
        return YES;
    }
  

  }
  if (texttitle.length >13) {
  return NO;
  }
  [textField setText:texttitle];
  [self.loginButton setImage:[UIImage imageNamed:@"zhihuiButtonlogin"] forState:UIControlStateNormal];
  self.loginButton.userInteractionEnabled = NO;
  return NO;
  }