輸入框TextField首位禁止輸入0或._uitextfield

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{    if ([textField.text rangeOfString:@"."].location == NSNotFound)    {        isHaveDian = NO;    }    if ([string length] > 0)    {        unichar single = [string characterAtIndex:0];//當前輸入的字元        if ((single >= '0' && single <= '9') || single == '.')//資料格式正確        {            //首字母不能為0和小數點            if([textField.text length] == 0)            {                if(single == '.')                {                    [self showMyMessage:@"親，第一個數字不能為小數點!"];                    [textField.text stringByReplacingCharactersInRange:range withString:@""];                    return NO;                }                if (single == '0')                {                    [self showMyMessage:@"親，第一個數字不能為0!"];                    [textField.text stringByReplacingCharactersInRange:range withString:@""];                    return NO;                }            }            //輸入的字元是否是小數點            if (single == '.')            {                if(!isHaveDian)//text中還沒有小數點                {                    isHaveDian = YES;                    return YES;                }else{                    [self showMyMessage:@"親，您已經輸入過小數點了!"];                    [textField.text stringByReplacingCharactersInRange:range withString:@""];                    return NO;                }            }else{                if (isHaveDian) {//存在小數點                    //判斷小數點的位元                    NSRange ran = [textField.text rangeOfString:@"."];                    if (range.location - ran.location <= 2) {                        return YES;                    }else{                        [self showMyMessage:@"親，您最多輸入兩位小數!"];                        return NO;                    }                }else{                    return YES;                }            }        }else{//輸入的資料格式不正確            [self showMyMessage:@"親，您輸入的格式不正確!"];            [textField.text stringByReplacingCharactersInRange:range withString:@""];            return NO;        }    }    else    {        return YES;    }}-(void)showMyMessage:(NSString*)aInfo {    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"提示" message:aInfo delegate:self cancelButtonTitle:@"確定" otherButtonTitles:nil, nil];    [alertView show];}