Monday, May 23, 2011

Universal iOs Applications

I've spent this afternoon looking at building a universal application for an iPhone application.

First of all I would like to go on the record that I think in general this is a bad software engineering practice - at least in theory .

Having your code check to see if what kind of device it is running and then execute a different set of functions based on the answer feels very hackish to me - at least from a conceptual level.

However, from a user perspective it is sweet software magic that is incredibly awesome - especially when dealing with "markets" similar to what Apple and Google have. For example you only can buy an application once and it can be run on the iPhone or iPad. It's like getting two great applications for the price of one.

I finally decided to buckle down and work through this and as you may expect it is much easier than I expected it to be. I started by:

  • creating a brand new iPhone application
  • then clicked on Application in the top left pane
  • and selected "Universal" in the Deployment Target drop down

Here is a screen shot:

Once xCode runs through it's magic you get a new folder called iPad that contains a new "Window" called "MainWindow-iPad.xib".

Now if you run the application you will be able to run in full iPad mode but the layout will be used by both the iPhone and iPad emulator and that is not what I intended to happen... To get this to change first of all you need another ViewController for the iPad to run so go ahead and create one of those using:
File -> New -> New File... c'mon you know the rest...

So... how do we get our new controller instantiated? Probably have to link into the app delegate, check the InterfaceIdiom to find out what kind of device we're running right?

Nope - not at all. You can handle all of this magic in the Interface Designer. No code change is actually needed! Here is how to do it:
Click on the new "MainWindow-iPad.xib" that xCode created for us
Select the View object in the hierarchy
and change the class under the "Identity Inspector"

Now if you run it you will still get the old layout (and probably crash). What you have to do is tell interface builder to load a different nib file:

Now you can run either emulator and you will get the correct view controller magically instantiated and the correct nib will be laoded.

That doesn't feel very hackish at all now does it?