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)

Adding external parameter names

In the preceding examples in this section, we defined the parameters' names and value types in the same way we would define parameters in C code. In Swift, we are not limited to this syntax as we can also use external parameter names.

External parameter names are used to indicate the purpose of each parameter when we call a function. An external parameter name for each parameter needs to be defined in conjunction with its local parameter name. The external parameter name is added before the local parameter name in the function definition. The external and local parameter names are separated by a space.

Let's look at how to use external parameter names. But before we do, let's review how we have previously defined functions. In the following two examples, we will define a function without external parameter names, and then redefine...