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)

Type casting with protocols

Typecasting is a way to check the type of the instance and/or to treat the instance as a specified type. In Swift, we use the is keyword to check whether an instance is a specific type, and the as keyword to treat the instance as a specific type.

To start, let's see how we would check the instance type using the is keyword. The following example shows how this is done:

for person in people { 
   if let p = person as? SwiftProgrammer {  
    print("\(person.firstName) is a Swift Programmer") 
   } 
}

In this example, we use the if conditional statement to check whether each element in the people array is an instance of the SwiftProgrammer type and, if so, we print that the person is a Swift programmer to the console. While this is a good method to check whether we have an instance of a specific class or structure, it is not very efficient...