Foundational APIs include strings, collections, class introspection, threading, and basic object persistence. Foundational APIs are defined in the Foundation library, which your application is linked against. These APIs are shared across iOS and OS X applications.
NSLog, while not strictly an API, is a part of a foundational knowledge of Objective-C. It prints a format string (discussed shortly) to the Xcode console during debug (or the system log during normal execution). It is helpful for debugging and logging purposes.
In this chapter, you will learn about the core classes provided for working with the Objective-C language. You’ll see strings, arrays, sets, and more, and you will learn about threading, run ...