Chapter 1, Starting with the Protocol, looks at what protocols are and how they are used in the Swift programming language. We will also examine how the protocol can be used to write very flexible and reusable code.

Chapter 2, Our Type Choices, discusses the different types that Swift offers (structs, classes, enums, and tuples). We will look at several examples of when to use the various types and when not too.

Chapter 3, Extensions, looks at how extensions and protocol extensions are used with the Swift programming language. We will look at examples of how extensions can be used with protocol-oriented programming.

Chapter 4, Generics, Apple has stated that Generics is one of the most powerful features of Swift and this chapter will show how powerful Generics is. We will look at how to use Generics to make very flexible types, and also how to implement the Copy-on-Write feature for our custom types.

Chapter 5, Object-Oriented Programming, examines how we would develop characters for a video game, taking an object-oriented approach. In order to really appreciate the ideas behind protocol-oriented programming, we need to understand the problems it is designed to solve. We will then look at the drawbacks with this design.

Chapter 6, Protocol-Oriented Programming, develops the same video game characters from chapter 5, but this time we will take a protocol-oriented approach to the design. We will then compare the object-oriented approach and the protocol-oriented approach to see the advantages that the protocol-oriented approach offers.

Chapter 7, Adopting Design Patterns in Swift, looks at implementing several design patterns using protocol-oriented programming. For each of the design patterns, we will look at the problem they are designed to solve and how to implement the pattern.

Chapter 8, Case Studies, explores two case studies. This chapter is designed to pull everything from the first six chapters together to show the reader how to use protocol-oriented programming in real-world situations.

To follow along with the examples in this book, the reader will need to have an Apple computer with OS X 10.13 or higher installed. They will also need to install XCode version 9.0 or higher with Swift version 4 or higher. The reader should possess at least basic knowledge of the Swift programming language.

This book is intended for the developer who has at least an introductory knowledge of the Swift programming language and wants to understand what protocol-oriented programming is. This book is written for the developer that not only wants to understand protocol-oriented programming but also wants to fully understand the different components of the programming paradigm. This book is written for the developer who learns best by looking at and working with code, because every concept covered in the book is backed by example code written to give the reader a solid understanding of the current topic and to demonstrate how to properly implement it.

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "With the where clause we are requiring that the elements in the iterator, within the E type, must be of the Integer type"

A block of code is set as follows:

protocol ZombieObserver {  
  func turnLeft() 
  func turnRight()  
  func seesUs() 
} 

Any command-line input or output is written as follows:

Making a copy of internalQueue

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "From this menu, we will want to select theCreate a new Xcode projectoption."

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