ios判断设备是iphone还是ipad

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions
{
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
// Override point for customization after application launch.
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
        self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController_iPhone"bundle:nil] autorelease];
    } else {
        self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController_iPad"bundle:nil] autorelease];
    }
    self.window.rootViewController = self.viewController;
    [self.window makeKeyAndVisible];
return YES;
}