iPhone Open Application Development

Transitioning to Objective-C

Objective-C was written in the early 1980s by scientist and software engineer Brad Cox. It was designed as a way of introducing the capabilities of the Smalltalk language into a C programming environment. A majority of the iPhone's framework libraries are written in Objective-C, but because the language was designed to accommodate the C language, you can use C and C++ in your application as well. Objective-C is used primarily on Mac OS X and GNUstep (a free OpenStep environment). Many languages, such as Java and C#, have borrowed from the Objective-C language. The Cocoa framework makes heavy use of Objective-C on the Mac desktop, which carried over onto the iPhone.

If you've developed on the Mac OS X desktop before, you're already familiar with Objective-C, but if the iPhone is your first Apple platform, then you're likely transitioning from C or C++. This section will cover some of the more significant differences between these languages. If you have a prior background in C or C++, this should be enough to get you up and writing code using the examples in this book as a guide.

Messaging

The first thing you'll notice in Objective-C is the heavy use of brackets. In Objective-C, methods are not called in a traditional sense; instead, they are sent messages. Likewise, a method doesn't return, but rather responds to the message. Unlike C, where function calls must be predefined, Objective-C's messaging style allows the developer to dynamically create new methods ...