Two Languages in One
Objective-C was designed as a strict superset of C, which means that any C program is also a valid Objective-C program. The Objective-C designers decided to keep the C language intact and add special syntax for object-oriented features to make it easy to distinguish between the two. Also retained from C is division of the code for each class into two files: a header file with a .h extension that defines publicly available interface of methods and properties for the class and a method file with a .m extension that defines the implementation of the methods. If you have read any of the iOS chapters, you have already seen these files in your project.
The following is a brief overview of some of the coding constructs that the ...
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