iPhone® Application Development All-In-One For Dummies®

Chapter 5. Extending Your App with a Photo View

In This Chapter

• Using polymorphism to add a new Photo view

• Setting up horizontal scrolling between views

• Creating subclasses of UIView and UIViewController

• Animating the photo view

• Accessing photos and other media on the iPhone

• Adding an application icon

One reason why it's easy to extend and enhance your iPhone app is the fact that the template sets you up to take advantage of delegation — you're using a behavior-rich object supplied by the framework as is, and you're putting the code for program-specific behavior in a separate (delegate) object. You're basically using delegation to get the framework objects to do the work for you.

Government and military leaders know all about delegation. Ronald Reagan could have been talking about extending the functionality of apps object-oriented programming when he said "Surround yourself with the best people you can find, delegate authority, and don't interfere." And General George S. Patton seemed to know all about combining delegation with encapsulation to enhance applications when he said, "Never tell people how to do things. Tell them what to do and they will surprise you with their ingenuity."

When you combine delegation, encapsulation, and inheritance, changing or enhancing objects or their functionality becomes much easier because it reduces the impact of those changes on the rest of your application. As I point out in Chapter 1 of Book II, inheritance allows you to do a number of things that ...