Who Should Read This Book
If you want to develop native apps for Mac OS X or for iOS, the language in which you write them is Objective-C. (You can write web-based apps using Apple’s Dashcode and Safari extensions.)
Because Apple’s development environment builds on the frameworks of Cocoa and Cocoa Touch, what you have to write is the code that is specific to your own app. All of the basic functionality is provided by Cocoa and the frameworks; you do not have to write any code to manage menus for example (in most cases). The code that you write is very specific code that fits into the existing frameworks. It might be code that overrides or extends an existing method, or it might be new methods that are unique to your own app.