Table Of ContentSwift 3 Protocol-Oriented
Programming
Second Edition
Build fast and powerful applications with the power of
protocol-oriented programming
Jon Hoffman
BIRMINGHAM - MUMBAI
Swift 3 Protocol-Oriented Programming
Second Edition
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First published: February 2016
Second edition: November 2016
Production reference: 1231116
Published by Packt Publishing Ltd.
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Credits
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Jon Hoffman Safis Editing
Reviewer Project Coordinator
Andrea Prearo Shweta H Birwatkar
Commissioning Editor Proofreader
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About the Author
Jon Hoffman has over 20 years of experience in the field of information technology. Over
those 20 years, Jon has worked in the areas of system administration, network
administration, network security, application development, and architecture. Currently, Jon
works as a senior software engineer for Syn-Tech Systems.
Jon has developed extensively for the iOS platform since 2008. This includes several apps
that he has published in the App Store, apps that he has written for third parties, and
numerous enterprise applications. What really drives Jon is the challenges the information
technology field provides and there is nothing more exhilarating to him than overcoming a
challenge.
You can follow Jon on his two blogs: http://masteringswift.blogspot.com and http
://myroboticadventure.blogspot.com.
Some of Jon’s other interests are watching baseball (Go Sox) and basketball (Go Celtics). Jon
also really enjoys Tae Kwon Do where he and his oldest daughter Kailey earned their black
belts together early in 2014, Kim (his wife) earned her black belt in December 2014, and his
youngest daughter is currently working towards her black belt.
I would like to thank my wonderful wife, Kim, without whose support, encouragement,
patience, and understanding, this book would have never been written. I would also like to
thank my two wonderful daughters, Kailey and Kara, who have both been my inspiration
and driving force since the days they were born.
About the Reviewer
Andrea Prearo is a software engineer with over 15 years of experience.
He is originally from Italy, and after a decade of writing software in C/C++ and C#, he
moved to the Bay Area in 2011 to start developing mobile apps.
In the last few years, he has been focusing on Swift, Objective-C, iOS, and microservices,
with some short explorations of the Android platform.
Currently, he is a member of the iOS development team at Capital One, working on the
company’s flagship mobile banking app.
His interests include reading books, watching movies, and hiking. From time to time, he
also blogs about tech on Medium: https://medium.com/@andrea.prearo.
I would like to thank my wonderful wife, Nicole, for her never-ending support in all my
endeavors.
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Table of Contents
Preface
1
Chapter 1: Object-Oriented and Protocol-Oriented Programming
7
What is object-oriented programming? 8
Requirements for the sample code 9
Swift as an object-oriented programming language 10
Drawbacks to object-oriented design 17
Swift as a protocol-oriented programming language 18
Summarizing protocol-oriented programming and object-oriented
programming 25
Differences between object-oriented programming and protocol-
oriented programming 26
Protocol and protocol extensions compared with superclasses 27
Implementing vehicle types 30
The winner is… 31
Summary 32
Chapter 2: Our Type Choices
33
The class 35
The structure 36
Access controls 37
The enumerations 38
The tuple 43
Protocols 45
Value and reference types 45
Recursive data types for reference types only 51
Inheritance for reference types only 54
Swift's built-in data types and data structures 56
Summary 58
Chapter 3: Catching Our Errors
59
Using the guard statement 60
Error handling 63
Error handling with return values 63
Error handling with do-catch 66
Representing errors 66
Throwing errors 68
Catching errors 71
Using the defer statement 74
When to use error handling 74
Summary 76
Chapter 4: All About the Protocol
77
Protocol syntax 79
Defining a protocol 79
Property requirements 80
Method requirements 81
Optional requirements 81
Protocol inheritance 82
Protocol composition 83
Using protocols as a type 86
Polymorphism with protocols 88
Type casting with protocols 89
Associated types with protocols 90
Delegation 93
Designing and developing with protocols 96
Summary 100
Chapter 5: Lets Extend Some Types
101
Defining an extension 102
Protocol extensions 105
Text validation 110
Summary 117
Chapter 6: Working with Generics
118
Generic functions 119
Type constraints with generics 122
Generic types 123
Associated types 127
Generics in a protocol-oriented design 128
Summary 133
Chapter 7: Adopting Design Patterns in Swift
134
What are design patterns? 135
Creational patterns 136
The singleton design pattern 137
Understanding the problem 137
Understanding the solution 138
[ ii ]
Implementing the singleton pattern 138
The builder design pattern 140
Understanding the problem 140
Understanding the solution 140
Implementing the builder pattern 141
The factory method pattern 146
Understanding the problem 146
Understanding the solution 146
Implementing the factory method pattern 147
Structural design patterns 150
The bridge pattern 150
Understanding the problem 150
Understanding the solution 151
Implementing the bridge pattern 151
The facade pattern 155
Understanding the problem 155
Understanding the solution 155
Implementing the facade pattern 156
The proxy design pattern 158
Understanding the problem 158
Understanding the solution 159
Implementing the proxy pattern 159
Behavioral design patterns 161
The command design pattern 162
Understanding the problem 162
Understanding the solution 162
Implementing the command pattern 162
The strategy pattern 165
Understanding the problem 165
Understanding the solution 165
Implementing the strategy pattern 165
The observer pattern 167
Understanding the problem 167
Understanding the solution 168
Implementing the observer pattern 168
Summary 173
Chapter 8: Case Studies
174
Logging service 175
Requirements 176
The design 176
Conclusion 185
Data access layer 186
Requirements 186
[ iii ]
