Is it safe to check for UI_USER_INTERFACE_IDIOM() to determine if it's an iPhone or iPad?

I've found this code, here:

if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        str = [NSString stringWithString:@"Running as an iPad application"];
    } else {
        str = [NSString stringWithString:
                  @"Running as an iPhone/iPod touch application"];
    }

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Platform"
 开发者_运维技巧                                                   message:str
                                                   delegate:nil
                                          cancelButtonTitle:@"OK" 
                                          otherButtonTitles:nil];
    [alert show];
    [alert release];   

How safe is this check? Does Apple actually recommend doing this? Or can it happen that it won't detect an iPad as iPad, or iPhone as iPhone?

It should be safe enough, it's well-documented by Apple.

That is just shorthand for the following code:

if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {
// etc

It could conceivably fail if you tried to run this on anything less than iOS 3.2 (as it was only introduced then), but this might not be an issue for you.