UITextField 限制只能输入数字和小数点，只能有两位小数

- (BOOL)textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)string {         if (textField == _dosageTextField)  {
        if([textField.textrangeOfString:@"."].location== NSNotFound) {
                     isHaveDian = NO;
                 }
             if([string length] > 0) {
           
                    unichar single = [stringcharacterAtIndex:0];//当前输入的字符
                     if ((single >= '0' && single <= '9') || single == '.') {//数据格式正确
               
                            //首字母不能为0和小数点
                            if([textField.textlength] == 0){
                                     if(single == '.') {
                                             [selfshowError:@"亲，第一个数字不能为小数点"];
                                            [textField.textstringByReplacingCharactersInRange:rangewithString:@""];
                                            returnNO;
                                         }
                                     if (single == '0') {
                                             [selfshowError:@"亲，第一个数字不能为0"];
                                             [textField.textstringByReplacingCharactersInRange:rangewithString:@""];
                                             returnNO;
                                         }
                                 }
               
                             //输入的字符是否是小数点
                             if (single == '.') {
                                     if(!isHaveDian)//text中还没有小数点
                                         {
                                                 isHaveDian = YES;
                                                 returnYES;
                           
                                             }else{
                                                     [selfshowError:@"亲，您已经输入过小数点了"];
                                                     [textField.textstringByReplacingCharactersInRange:rangewithString:@""];
                                                     returnNO;
                                                 }
                                 }else{
                                         if (isHaveDian) {//存在小数点
                           
                                                 //判断小数点的位数
                                                 NSRange ran = [textField.textrangeOfString:@"."];
                                                 if (range.location- ran.location<= 10) {
                                                         returnYES;
                                                     }else{
                                                           [selfshowError:@"亲，您最多输入两位小数"];
                                                             returnNO;
                                                         }
                                             }else{
                                                     returnYES;
                                                 }
                                    }
                         }else{//输入的数据格式不正确
                                 [selfshowError:@"亲，您输入的格式不正确"];
                                 [textField.textstringByReplacingCharactersInRange:rangewithString:@""];
                                 returnNO;
                             }
                }
             else
                 {
                    returnYES;
                }
    }
    returnYES;
}

- (void)showError:(NSString*)errorString {
     [selfrsva_presentViewControllerWithMessage:errorString]; }
- (void)rsva_presentViewControllerWithMessage:(NSString*)message {
   
    UIAlertController*alertController = [RSMethodylg_presentAlertControllerWithTitle:@"提示"message:message];
    [selfpresentViewController:alertControlleranimated:YEScompletion:nil]; }