Book Image

Mastering Swift 5 - Fifth Edition

By : Jon Hoffman
Book Image

Mastering Swift 5 - Fifth Edition

By: Jon Hoffman

Overview of this book

Over the years, the Mastering Swift book has established itself amongst developers as a popular choice as an in-depth and practical guide to the Swift programming language. The latest edition is fully updated and revised to cover the new version: Swift 5. Inside this book, you'll find the key features of Swift 5 easily explained with complete sets of examples. From the basics of the language to popular features such as concurrency, generics, and memory management, this definitive guide will help you develop your expertise and mastery of the Swift language. Mastering Swift 5, Fifth Edition will give you an in-depth knowledge of some of the most sophisticated elements in Swift development, including protocol extensions, error handling, and closures. It will guide you on how to use and apply them in your own projects. Later, you'll see how to leverage the power of protocol-oriented programming to write flexible and easier-to-manage code. You will also see how to add the copy-on-write feature to your custom value types and how to avoid memory management issues caused by strong reference cycles.
Table of Contents (20 chapters)

Using optionals

The key to using optionals is to always verify that they contain a valid value prior to accessing them. We use the term unwrapping to refer to the process of retrieving a value from an optional.

Forced unwrapping of an optional

To unwrap or retrieve the value of an optional, we place an exclamation mark (!) after the variable name. This is called forced unwrapping. Forced unwrapping, in this manner, is very dangerous and should be used only if we are certain that the variable contains a non- nil value. Otherwise, if it does contain a nil value, we will get a runtime error and the application will crash.

When we use the exclamation point to unwrap an optional, we are telling the compiler that we know the optional...