Swift Programming: The Big Nerd Ranch Guide

Whither Objective-C?

So, what about Objective-C, Apple’s previous lingua franca for its platforms? Do you still need to know that language? For the time being, we think that answer is an unequivocal “Yes.” Apple’s Cocoa library, which you will use extensively, is written in Objective-C, so debugging will be easier if you understand that language. Moreover, most learning materials and existing Mac and iOS apps are written in Objective-C. Indeed, Apple has made it easy, and sometimes preferable, to mix and match Objective-C with Swift in the same project. As an iOS or Mac developer, you are bound to encounter Objective-C, so it makes sense to be familiar with the language.

But do you need to know Objective-C to learn Swift? Not at all. ...