Learning Swift

266 Pages·2015·2.624 MB·English

by  Andrew J Wagner

Learning Swift
Build a solid foundation in Swift to develop smart and
robust iOS and OS X applications
Andrew J Wagner
BIRMINGHAM - MUMBAI
Learning Swift
Copyright © 2015 Packt Publishing
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First published: June 2015
Production reference: 1250615
Published by Packt Publishing Ltd.
Livery Place
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Birmingham B3 2PB, UK.
ISBN 978-1-78439-250-5
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Credits
Author Project Coordinator
Andrew J Wagner Nidhi Joshi
Reviewers Proofreader
Giordano Scalzo Safis Editing
Cory Bohon
Indexer
Mariammal Chettiyar
Commissioning Editor
Sarah Crofton
Graphics
Disha Haria
Acquisition Editors
Vivek Anantharaman
Richard Brookes-Bland Production Coordinator
Nilesh R. Mohite
Content Development Editor
Kirti Patil Cover Work
Nilesh R. Mohite
Technical Editor
Mrunmayee Patil
Copy Editors
Pranjali Chury
Neha Vyas
About the Author
Andrew J Wagner is an independent software developer who concentrates on iOS
development and backend web services and has a degree in computer engineering
from Rensselaer Polytechnic Institute, New York. He has also been developing
his own iOS apps through his company, Learn Brigade LLC, since 2008 and has
experience working with and for large-scale companies and small-scale companies.
He is passionate about using computers as a creative outlet and writing software that
is beautiful in implementation, functionality, and experience.
About the Reviewer
Giordano Scalzo has been a developer since the days of the ZX Spectrum.
He worked with C++, Java, .NET, Ruby, Python, and a ton of other languages he has
forgotten the names of. After years of backend development and a hiatus from the
technical side when he worked as a project manager, he is currently a freelancer in
London where, through his company, Effective Code Ltd, he delivers code for iOS
aiming at quality and reliability.
In his spare time, when he is not crafting retro game clones for iOS, he writes his
thoughts on his blog at http://giordanoscalzo.com.
I'd like to thank my better half, Valentina, who lovingly supports me
in everything I do—without you, none of this would have
been possible.
I would also like to thank my children, Mattia and Luca, who
are my future and have given me lots of smiles and hugs when
I needed them.
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Table of Contents
Preface vii
Chapter 1: Introducing Swift 1
Defining our goals for this book 1
Setting up the development environment 2
Running our first Swift code 3
Understanding playgrounds 5
Learning with this book 6
Summary 6
Chapter 2: Building Blocks – Variables, Collections,
and Flow Control 7
Core Swift types 8
Constants and variables 8
Containers 8
Tuples 9
Arrays 9
Dictionaries 10
Swift's type system 11
Printing on the console 13
Control flow 14
Conditionals 14
Switches 15
Loops 18
Functions 21
Basic functions 21
Parameterized functions 22
Functions that return values 23
Functions with default arguments 25
Bringing it all together 26
Summary 31
[ i ]
Table of Contents
Chapter 3: One Piece at a Time – Types, Scopes, and Projects 33
Structs 34
Types versus instances 34
Properties 35
Member and static methods 36
Computed properties 40
Reacting to property changes 41
Subscripts 42
Custom initialization 43
Classes 46
Inheriting from another class 46
Initialization 48
Overriding initializers 49
Required initializers 49
Designated and convenience initializers 50
Overriding methods and computed properties 51
Methods 52
Computed properties 53
Casting 53
Upcasting 54
Downcasting 55
Enumerations 56
Basic declaration 56
Testing enumeration values 56
Raw values 57
Associated values 58
Methods and properties 60
Projects 61
Setting up a command-line Xcode project 62
Creating and using an external file 64
Interfacing with code from other files 65
File organization and navigation 68
Extensions 69
Scope 70
How is scope defined 70
Nested types 70
Access control 71
Summary 72
Chapter 4: To Be or Not to Be – Optionals 73
Introducing optionals 74
Unwrapping an optional 75
Optional binding 75
[ ii ]
Table of Contents
Forced unwrapping 77
Nil coalescing 78
Optional chaining 78
Implicitly unwrapped optionals 80
Debugging optionals 82
The underlying implementation 85
Summary 86
Chapter 5: A Modern Paradigm – Closures and Functional
Programming 87
Functional programming philosophy 88
State and side effects 88
Declarative versus imperative code 89
Closures 90
Closures as variables 90
Closures as parameters 91
Syntactic sugar 92
Building blocks of functional programming in Swift 94
The filter function 94
The reduce function 94
The map function 96
The sorted function 96
How these affect the state and nature of code 97
Lazy evaluation 97
Curried functions 98
Summary 100
Chapter 6: Make Swift Work for You – Protocols and Generics 101
Protocols 101
Defining a protocol 102
Implementing a protocol 102
Using type aliases 104
Defining a generic 106
The generic function 106
The generic type 108
Type constraints 109
Protocol constraints 109
Where clauses for protocols 111
Where clauses for equality 112
Extending the existing generics 112
Enhancing arrays 113
Enhancing dictionaries 114
[ iii ]