Book Image

Learn Scala Programming

By : Slava Schmidt
Book Image

Learn Scala Programming

By: Slava Schmidt

Overview of this book

The second version of Scala has undergone multiple changes to support features and library implementations. Scala 2.13, with its main focus on modularizing the standard library and simplifying collections, brings with it a host of updates. Learn Scala Programming addresses both technical and architectural changes to the redesigned standard library and collections, along with covering in-depth type systems and first-level support for functions. You will discover how to leverage implicits as a primary mechanism for building type classes and look at different ways to test Scala code. You will also learn about abstract building blocks used in functional programming, giving you sufficient understanding to pick and use any existing functional programming library out there. In the concluding chapters, you will explore reactive programming by covering the Akka framework and reactive streams. By the end of this book, you will have built microservices and learned to implement them with the Scala and Lagom framework.

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Table of Contents (19 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Get in touch
Free Chapter
1
An Introduction to Scala 2.13
An Introduction to Scala 2.13
Technical requirements
Introduction to Scala 2.13
New features of Scala 2.13
The Scala 2.13 Collection Library
Summary
Questions
Further reading
2
Understanding Types in Scala
Understanding Types in Scala
Technical requirements
Understanding types
Types – all the way down
Using types to define domain constraints
Summary
Questions
Further reading
3
Deep Dive into Functions
Deep Dive into Functions
Technical requirements
Ways to define a function
Polymorphism and higher order functions
Recursion and trampolining
Object-oriented aspects of functions
Summary
Questions
Further reading
4
Getting to Know Implicits and Type Classes
Getting to Know Implicits and Type Classes
Technical requirements
Types of implicits
View and context bounds
Type classes
Implicit scope resolution
Summary
Questions
Further reading
5
Property-Based Testing in Scala
Property-Based Testing in Scala
Technical requirements
Introduction to property-based testing
Properties
Generators
Summary
Questions
6
Exploring Built-In Effects
Exploring Built-In Effects
Technical requirements
Introduction to effects
Option
Either
Try
Future
Summary
Questions
7
Understanding Algebraic Structures
Understanding Algebraic Structures
Technical requirements
Introduction to abstract algebraic structures
Semigroup
Monoid
Foldable
Group
Summary
Questions
Further reading
8
Dealing with Effects
Dealing with Effects
Technical requirements
Functor
Applicative
Traversable
Summary
Questions
Further reading
9
Familiarizing Yourself with Basic Monads
Familiarizing Yourself with Basic Monads
Technical requirements
Introduction to monads
Id Monad
State monad
Reader monad
Writer monad
Summary
Questions
Further reading
10
A Look at Monad Transformers and Free Monad
A Look at Monad Transformers and Free Monad
Technical requirements
Combining monads
Monad transformers
Monad transformers stacks
Free monads
Summary
Questions
Further reading
11
An Introduction to the Akka and Actor Models
An Introduction to the Akka and Actor Models
Technical requirements
Introduction to the actor model
Akka basics
Advanced topics
Testing actors
Running the application
Summary
Questions
Further reading
12
Building Reactive Applications with Akka Typed
Building Reactive Applications with Akka Typed
Technical requirements
Introduction
Akka Typed basics
Akka Typed – beyond the basics
Testing
Running the application
Summary
13
Basics of Akka Streams
Basics of Akka Streams
Technical requirements
Introduction to Akka Streams
Basics of Akka Streams
Testing
Running the application
Summary
Questions
Further reading
14
Project 1 - Building Microservices with Scala
Project 1 - Building Microservices with Scala
Technical requirements
Essentials of microservices
Building a microservice with http4s and doobie
Building microservices with Akka-HTTP and Akka Persistence
Summary
Questions
Further reading
15
Project 2 - Building Microservices with Lagom
Project 2 - Building Microservices with Lagom
Technical requirements
Why Lagom?
Project overview and setup
Lagom's APIs
Running the application
Testing
Summary
Questions
Further reading
16
Preparing the Environment and Running Code Samples
Preparing the Environment and Running Code Samples
Installing software
Working with the code
17
Assessments
Assessments
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
Chapter 13
Chapter 14
Chapter 15
18
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Running the application

Now, we have all of our services built together and can run the project as a whole using the runAll command as before. We also need to have an Akka-HTTP example from the previous chapter running and have enough inventory so that the boy can get some groceries from it:

The previous screenshot shows two Terminal windows: on the right the Akka HTTP shop from Chapter 14 is running and on the left the runAll command is ready to be executed. The runAll command takes some time to start all of the subsystems and produces a lot of output in the console.

At the moment of this writing the processing pipeline stopped just before returning baked cookies to the manager. We reported this issue as a Lagom bug (https://github.com/lagom/lagom/issues/1616) but unfortunately got no feedback from Lagom team yet. We left the example as it is with the hope that the issue will...
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