Part 3. Making maximum use of framework functionality

If every iOS application had to reinvent the wheel, there would be significantly fewer applications in the iTunes App Store, because developers would waste time recreating classes to perform similar functionality. The Cocoa Touch environment provides a number of support libraries and classes that, with a few simple lines of code, enable fairly powerful and complex behavior to be available for application developers to use. To quickly come to market, and focus more time on the aspects of your applications that make it unique, it’s important for application developers to know what kind of services the iOS SDK provides, and how to take advantage of them.

This part of the book begins by showing how Objective-C frameworks typically handle error conditions and exceptions. It then takes a deep dive into two semi-related technologies, called Key Value Coding (KVC) and NSPredicate, that allow flexible sorting and filtering to be introduced within your applications. These two technologies also demonstrate how certain knowledge can be reutilized, as shown in the discussion about using Core Data to work with databases using KVC and NSPredicate.