Learning the iOS 4 SDK for JavaScript Programmers

Chapter 4. Structural Overview of an iOS App

Now that we have a working iOS app, we can look more closely at many of the details in the source code for that app and the project. Xcode will again be your gateway to the inner workings. Although the title of this chapter doesn’t mention object-oriented programming (OOP), this chapter is where you will learn the fundamentals—especially the terminology, which is often quite different from what you’ve seen in the JavaScript world. Despite the differences in naming, you will recognize some familiar concepts.

Where It All Begins: APIs

An application programming interface, or API, is essentially a list of entities you can program and what you can ask those entities to do in a program. Designers of computers and software systems can choose to expose the inner workings of those devices and programs to third-party programmers. APIs typically shield the third-party programmer from the complex inner workings of the systems and provide him with simpler, optimized, and well-tested ways to control those systems.

APIs You Already Know

As a client-side scripter, you have already worked with a number of APIs, even if the three-letter term wasn’t forced upon you. The API most obvious to you should be the DOM, which exposes every type of HTML element as an object you can script. The authors of the W3C DOM write specifications about how objects are named, what their properties and methods are, and how objects are to behave under script control. The initial ...