Differentiate iPhone4 vs. iPodTouch4 in Code

I want to programmatically differentiate between iPhone4 and iTouch4. Here is what I have tried :

+(BOOL) isIphone4 {
     if ( ![ImagePicker isIpodTouch4] ) {
          return NO;
     }

     if ([UIImagePickerController respondsToSelector:@selector(isFlashAvailableForCameraDevice:)]) {
   开发者_如何学运维       if ([UIImagePickerController isFlashAvailableForCameraDevice:UIImagePickerControllerCameraDeviceRear]) {
               return YES;
          }
     }
     return NO;
}

+(BOOL) isIpodTouch4 {
     if ([UIImagePickerController respondsToSelector:@selector(isCameraDeviceAvailable:)] ) {
          if ([UIImagePickerController isCameraDeviceAvailable:UIImagePickerControllerCameraDeviceFront]) {
               return YES;
          }
     }
     return NO;
}

However, seems like iPod Touch 4 is also passing the test for iPhone4. Does anyone have any ideas?

Thanks.

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This is similar:

Determine device (iPhone, iPod Touch) with iPhone SDK

The code example included allows you to tell the exact device.