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)

Inout parameters

If we want to change the value of a parameter and we want those changes to persist once the function ends, we need to define the parameter as an inout parameter. Any changes made to an inout parameter are passed back to the variable that was used in the function call.

Two things to keep in mind when we use inout parameters are that these parameters cannot have default values and that they cannot be variadic parameters.

Let's look at how to use the inout parameters to swap the values of two variables:

func reverse(first: inout String, second: inout String) {  
  let tmp = first 
  first = second  
  second = tmp 
} 

This function will accept two parameters and swap the values of the variables that are used in the function call. When we make the function call, we put an ampersand (&) in front of the variable name, indicating that the function can modify...