Professional Scala

232 Pages·2016·5.272 MB·English

by  Bedrytski, Aliaksandr, Bogucki, Janek, Detrich, Matthew de, Lacava, Alessandro, Neil, Benjamin

PROFESSIONAL SCALA
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
CHAPTER 1 Language Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
CHAPTER 2 Functional Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
CHAPTER 3 Java Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
CHAPTER 4 Simple Build Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
CHAPTER 5 Maven . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
CHAPTER 6 Scala Style/Lint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
CHAPTER 7 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
CHAPTER 8 Documenting Your Code with Scaladoc . . . . . . . . . . . . . . . . . . . . . . 95
CHAPTER 9 Type System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
CHAPTER 10 Advanced Functional Programming . . . . . . . . . . . . . . . . . . . . . . . . 165
CHAPTER 11 Concurrency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
CHAPTER 12 Scala.js . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
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PROFESSIONAL
Scala
Aliaksandr Bedrytski
Janek Bogucki
Alessandro Lacava
Matthew de Detrich
Benjamin Neil
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Professional Scala
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Copyright © 2016 by John Wiley & Sons, Inc., Indianapolis, Indiana
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ffi rs.indd 05/12/2016 Page iv
ABOUT THE AUTHORS
ALIAKSANDR BEDRYTSKI is a passionate software engineer at Worldline Lyon, France. Even though
it’s been more than four years since he discovered Scala, he’s still in love with the language and is
trying to push its boundaries every day. In his spare time he’s learning something new about space,
physics, and bleeding edge technologies. He is currently working as a lead developer on a data-
analysis project featuring Hadoop, Spark-Scala, Hive, and other Big Data tools. 
JANEK BOGUCKI is a co-founder at Inferess Inc. and principal consultant (Machine Learning and
Scala) at Combination One. He has a background in mathematics with an ongoing interest in com-
puter science, data science, machine learning, graph theory, and development methodologies. He
lives in Kent, UK with his wife Rebecca, son Theo, two cats, one dog, and a variable number of
chickens.
ALESSANDRO LACAVA holds a degree in telecommunications engineering. He’s had extensive
experience with OOP before becoming very passionate about functional programming. He is cur-
rently working as a lead designer and developer on different types of applications using mainly,
but not only, Scala. He’s also a contributor of pretty famous open source projects, such as shape-
less and cats.
MATTHEW DE DETRICH is a tech lead for Monetise Pty Ltd, where he primarily works on full stack
applications with backends written in Scala. Matthew has a passion for designing, building, and
integrating complex multi-domain systems from the ground up. In his spare time he is exploring
new developments in the Scala space, such as Scala.js.
BENJAMIN NEIL is a full stack engineer at AppThis LLC. He is a polyglot engineer who has had the
privilege of working the past eight years making websites, services, and tools for amazing compa-
nies. He is obsessed with Scala, Vim, DevOps, and making services scale smoothly.
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ABOUT THE TECHNICAL EDITORS
JACOB PARK is a Scala and Typesafe enthusiast; he embraces Akka, Play, and Spark, all with
Scala, to solve various problems regarding distributed systems with additional technologies such as
Cassandra and Kafka. As a believer in open-source software, he contributes to various projects on
GitHub related to Akka and Cassandra: https://github.com/jparkie. When he’s not working,
Jacob can be found at various Scala and Typesafe conferences and meetups, either as an attendee or
a presenter.
ARIEL SCARPINELLI is a senior Java developer at VirtualMind and is a passionate developer with
more than 15 years of professional experience. He currently leads four agile teams for a U.S.-based
enterprise SaaS company. He has experience in a lot of languages but is currently focused on Java
and JavaScript with some PHP and Python.
RADU GANCEA is a software engineer and consultant at Eloquentix with a Java background (also C/
C++). He is involved in projects in the energy and advertising sectors. His current focus is on Scala
and other JVM languages and frameworks.
ffi rs.indd 05/12/2016 Page vi
CREDITS
PROJECT EDITOR PROFESSIONAL TECHNOLOGY & STRATEGY
Charlotte Kughen DIRECTOR
Barry Pruett
TECHNICAL EDITORS
Jacob Park BUSINESS MANAGER
Ariel Scarpinelli Amy Knies
Radu Gancea
EXECUTIVE EDITOR
PRODUCTION EDITOR Jim Minatel
Barath Kumar Rajasekaran
PROJECT COORDINATOR, COVER
COPY EDITOR Brent Savage
Troy Mott
PROOFREADER
MANAGER OF CONTENT DEVELOPMENT Nancy Bell
AND ASSEMBLY
Mary Beth Wakefi eld INDEXER
Nancy Guenther
PRODUCTION MANAGER
Kathleen Wisor COVER DESIGNER
Wiley
MARKETING MANAGER
David Mayhew COVER IMAGE
©Sergey Nivens/Shutterstock
ffi rs.indd 05/12/2016 Page vii
CONTENTS
INTRODUCTION xv
CHAPTER 1: LANGUAGE FEATURES 1
Static Types and Type Inference 2
Implicit Parameters, Conversions, and Their Resolution 3
Case Class, Tuples, and Case Object 5
Abstract Class, Traits, and Sealed 6
Pattern Matching 8
Statements Are Expressions 9
String Interpolation 9
Scala Collections, immutable and mutable 10
For Comprehension 12
Packages, Companion Objects, Package Objects,
and Scoping 13
AnyVal, AnyRef, Any, and the Type Hierarchy 16
Summary 17
CHAPTER 2: FUNCTIONAL PROGRAMMING 19
Immutability 20
Pure Functions 22
Recursion 23
Higher-Order Functions 26
Core Collection Methods 27
Methods Returning a Collection 29
Methods Returning a Value 31
Currying and Partially Applied Functions 32
Null Handling (Option) 34
Strict versus Non-Strict Initialization 35
Summary 36
CHAPTER 3: JAVA COMPATIBILITY 37
Scala and Java Collections 37
Interfaces and Traits 40
Scala/Java Enumerations 42
Summary 43
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CONTENTS
CHAPTER 4: SIMPLE BUILD TOOL 45
Basic Usage 46
Project Structure 47
Single Project 47
Scopes 49
Custom Tasks 50
Dependencies 50
Resolvers 51
Advanced Usage 52
Advanced Dependencies 53
Testing in the Console 55
Release Management 56
Deploying to Sonatype 56
Packaging with SBT-Native-Packager 58
Creating a Docker Image 59
Common SBT Commands 60
Useful Plugins 61
Summary 62
CHAPTER 5: MAVEN 63
Getting Started with Maven and Scala 64
Introducing scala-maven-plugin 67
Adding Library Dependencies 70
Using the REPL 71
Getting Help 72
Running Tests 72
Joint Compilation with Java 74
Accelerating Compilation with Zinc 76
Summary 77
CHAPTER 6: SCALA STYLE/LINT 79
Scala with Style 79
Scaliform 81
Scapegoat 82
WartRemover 82
Scoverage 84
Summary 84
x
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CONTENTS
CHAPTER 7: TESTING 85
ScalaTest 86
Unit Tests 87
Integration Testing 87
Data-Driven Tests 88
Performance Testing 89
Acceptance Testing 90
Mocks 92
Load Testing 93
Summary 94
CHAPTER 8: DOCUMENTING YOUR CODE WITH SCALADOC 95
Why Document Your Code? 96
Revealing the Benefi ts 96
Bookending the Continuum 96
Choosing What to Document 96
Scaladoc Structure 97
Overall Layout 97
Index Pane 98
Content Pane 100
Invoking the Scaladoc Tool 106
Wiki Syntax 108
Formatting with Inline Wiki Syntax 108
Structuring with Block Elements 110
Linking 113
Locating Scaladoc 117
Tagging 117
Everyday Tagging 117
Tagging for Groups 123
Advanced Tagging 125
Invoking scaladoc: Additional Options 132
Integrating Scaladoc Creation with Your Project 133
Confi guring Maven 133
Confi guring SBT 134
Publishing Scaladoc 134
Tables and CSS 136
Summary 138
xi
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CONTENTS
CHAPTER 9: TYPE SYSTEM 139
What Is a Type System? 140
Static versus Dynamic Typing 140
What Static Type Systems Are Good For 141
What Dynamic Type Systems Are Good For 141
Scala’s Unifi ed Type System 141
Value Classes 143
Polymorphism 145
Subtype Polymorphism 145
Parametric Polymorphism 146
Ad Hoc Polymorphism 146
Bounds 149
Context Bounds 149
Upper and Lower Bounds 150
Variance 151
Other Niceties 155
Self-Type Annotations 155
Self-Recursive Types 158
Abstract Type Members 159
Dynamic Programming 161
Structural Types 161
Dynamic Trait 162
Summary 164
CHAPTER 10: ADVANCED FUNCTIONAL PROGRAMMING 165
Higher-Kinded Types 165
Functional Design Patterns 167
Functor 167
Applicative Functor 170
Monad 172
Semigroup 173
Monoid 174
Summary 176
CHAPTER 11: CONCURRENCY 179
Synchronize/Atomic Variables 181
Future Composition 184
Parallel Collections 187
Reactive Streams 192
STM 195
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