Book Image

Learning Swift Second Edition - Second Edition

By : Andrew J Wagner
Book Image

Learning Swift Second Edition - Second Edition

By: Andrew J Wagner

Overview of this book

Swift is Apple’s new programming language and the future of iOS and OS X app development. It is a high-performance language that feels like a modern scripting language. On the surface, Swift is easy to jump into, but it has complex underpinnings that are critical to becoming proficient at turning an idea into reality. This book is an approachable, step-by-step introduction into programming with Swift for everyone. It begins by giving you an overview of the key features through practical examples and progresses to more advanced topics that help differentiate the proficient developers from the mediocre ones. It covers important concepts such as Variables, Optionals, Closures, Generics, and Memory Management. Mixed in with those concepts, it also helps you learn the art of programming such as maintainability, useful design patterns, and resources to further your knowledge. This all culminates in writing a basic iOS app that will get you well on your way to turning your own app ideas into reality.
Table of Contents (19 chapters)
Learning Swift Second Edition
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Implicitly unwrapped optionals


There is a second type of optional called an implicitly unwrapped optional. There are really two ways to look at what an implicitly unwrapped optional is; one way is to say that it is a normal variable that can also be nil; the other way is to say that it is an optional that you don't have to unwrap to use. The important thing to understand about them is that, similar to optionals, they can be nil, but you do not have to unwrap them like a normal variable.

You can define an implicitly unwrapped optional with an exclamation mark (!) instead of a question mark (?) after the type name:

var name: String!

Similar to regular optionals, implicitly unwrapped optionals do not need to be given an initial value because they are nil by default.

At first it may sound like it is the best of both worlds, but in reality it is more like the worst of both worlds. Even though an implicitly unwrapped optional does not have to be unwrapped, it will crash your entire program if it is...