如何在iphone sdk中验证IP地址

Question

我有一个文本字段，用户可以在其中输入IP地址或任何网址。但问题是我只需要在用户输入IP地址时进行验证，如果他输入了URL，则不应该验证。

我完成的是：

-(BOOL)ipValidationUsingRegex:(NSString *)ipAddressStr
{
    NSString *ipValidStr = ipAddressStr;
    NSString *ipRegEx =
    @"^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])$";

    NSPredicate *regExPredicate =[NSPredicate predicateWithFormat:@"SELF MATCHES %@", ipRegEx];
    BOOL myStringMatchesRegEx = [regExPredicate evaluateWithObject:ipValidStr];

    NSLog(@"myStringMatchesRegEx = %d ",myStringMatchesRegEx);
    return myStringMatchesRegEx;
}



-(IBAction)saveAction:(id)sender
{
    if([msaTextField.text length] == 0 || [msrpTextField.text length] == 0)
    {
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Message" message:@"Please enter all fields" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alert show];
    }

    else
    {
    if(([msaTextField.text stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"0123456789."]].length > 0) ) {
        //URL
        NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
        // saving an NSString
        [prefs setObject:msaTextField.text forKey:@"MSA"];
        // saving an NSString
        [prefs setObject:msrpTextField.text forKey:@"MSRP"];

        [prefs synchronize];

        //[self.navigationController popViewControllerAnimated:YES];
        [self dismissModalViewControllerAnimated:YES];

        }
    else {
       //IP

        if(([self ipValidationUsingRegex:msaTextField.text] == YES) )
        {
            NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
            // saving an NSString
            [prefs setObject:msaTextField.text forKey:@"MSA"];
            // saving an NSString
            [prefs setObject:msrpTextField.text forKey:@"MSRP"];

            [prefs synchronize];

            //[self.navigationController popViewControllerAnimated:YES];
            [self dismissModalViewControllerAnimated:YES];
        }
        else 
        {
            UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Error" message:@"IP range is Invalid" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
            [alert show];
        }

    }
    }

}

我在这里遇到的问题是IP地址正确验证，但事情就是当我输入网址时，它也说Ip的无效范围作为警报。

我输入的网址类似于http://www.yahoo.com

请给我建议