UITextField 只输入数据跟小数点

UITextField 只输入数据和小数点
#define NUMBERS @"0123456789.\n"　　//匹配的字符，可以加入你想要的字符

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSCharacterSet *cs;       
    if(textField == self.userUsga)
    {
        cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBERS] invertedSet];       
        NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];       
        BOOL basicTest = [string isEqualToString:filtered];
        if(!basicTest)
        {
            UIAlertView* alert = [[UIAlertView alloc] initWithTitle:@"提示"
                                                            message:@"输入错误！"
                                                           delegate:nil
                                                  cancelButtonTitle:@"确定"
                                                  otherButtonTitles:nil];
           
            [alert show];
            [alert release];
            return NO;
        }   
    }

//其他的类型不需要检测，直接写入
return YES;       
}