ViewController关联iphone_xib和Ipad——xib两个xib

    MainViewController *mainVc =nil;

    // 判断是iPhone还是ipad

    if ([[UIDevicecurrentDevice] userInterfaceIdiom] ==UIUserInterfaceIdiomPhone) {

        mainVc = [[MainViewControlleralloc] initWithNibName:@"MainViewController-iphone"bundle:nil];

    }

    else

    {

        mainVc = [[MainViewController alloc] initWithNibName:@"MainViewController-ipad"bundle:nil];

    }

    self.window.rootViewController = mainVc;