Create single .xib for Universal app in Interface Builder? (iOS) - objective-c

Question

Apologies if this is a silly question, but I've done some googling and searched SO and haven't found anyone asking this exact question.
I have been doing iOS development for some time now, but I am completely new to the Interface Builder. What I want to know is this: is there any way to just create ONE .xib file and then use it for both iPhone and iPad in a Universal application?
It seems silly to me to have to create them separately; why do twice the work laying something out more than once in Interface Builder when I could do it once (with minor adjustments for screen size) in code?
Please let me know if I'm missing/misunderstanding something here. Like I said, I'm a complete Interface Builder newbie :)
EDIT: I have submitted non-interface-builder games to the App Store in the past where the iPhone and iPad versions were identical, so I'm not concerned with making the game look/feel different on each device. I intend for them to look exactly the same, aside from some slight positioning changes due to the difference in aspect ratio.

Answer 1

If you know what the resulting view would look like, based on autoresizing, you can indeed use only one .xib. May come in handy if the view is just some sort of a shared component that autoresizes as you want it to. However, if you need the view to look way different on iPad than on iPhone, just use two .xibs. It’s possible then to load the appropriate one as needed, for example in instance initializer, like this controller’s -init:
- (id)init
{
if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)
{
self = [super initWithNibName:#"YourNibForPad" bundle:nil];
}
else
{
self = [super initWithNibName:#"YourNibForPhone" bundle:nil];
}
if (self) { /* initialize other ivars */ }
return self;
}

Answer 2

The main reason that XIBs are separate files is because Apple feel that UIs designed for iPhones/iPod touches and iPads should be tailored to each respectively. This is echoed in their their iOS App Programming Guide, which says the following:
For views, the main modification is to redesign your view layouts to support the larger screen. Simply scaling existing views may work but often does not yield the best results. Your new interface should make use of the available space and take advantage of new interface elements where appropriate. Doing so is more likely to result in an interface that feels more natural to the user—and not just an iPhone app on a larger screen.
Whilst it can take time to maintain two XIBs for what is effectively one UI, I feel it is more straightforward than using one XIB and then having to connect up most of your UI elements in order to move them around programmatically when that XIB loads. After all, with two XIBs at least you can see what each UI looks like, and then make visual changes easily.
As an aside, don't forget iOS 5's Storyboards (read about them here), which make managing a view/view controller hierarchy much simpler.

Answer 3

Try to name them
MyCell.xib and MyCell ~ ipad.xib
then:
[self.tableView registerNib: #"MyCell" forCellReuseIdentifier: #"MyUniqueIdentifier"];

Answer 4

If your using IB, you need to create 2 separate xib files for iPhone and iPad. You need a separate iPad xib to make your app comply with the Apple iPad UI guidelines.