Book Image

Professional Scala

By : Mads Hartmann, Ruslan Shevchenko
Book Image

Professional Scala

By: Mads Hartmann, Ruslan Shevchenko

Overview of this book

This book teaches you how to build and contribute to Scala programs, recognizing common patterns and techniques used with the language. You’ll learn how to write concise, functional code with Scala. After an introduction to core concepts, syntax, and writing example applications with scalac, you’ll learn about the Scala Collections API and how the language handles type safety via static types out-of-the-box. You’ll then learn about advanced functional programming patterns, and how you can write your own Domain Specific Languages (DSLs). By the end of the book, you’ll be equipped with the skills you need to successfully build smart, efficient applications in Scala that can be compiled to the JVM.
Table of Contents (12 chapters)

Writing a Small DSL

In this section, we'll reimplement some FlatSpec ScalaTest DSLs in order to see how to implement DSLs in Scala.

First, we'll have a look at a simple way to model test cases in Scala using case classes. Then, we'll have a look at how to create a little DSL for creating those test cases.

Modeling Test Cases

Before we can create a DSL, we need to have something to create a DSL for. In our case, we want to create a DSL for specifying tests, so let's have a look at how we could model tests using case classes in Scala:

sealed trait TestResult
case class TestFailure(message: String) extends TestResult
case object TestSuccess extends TestResult

We'll create an algebraic data type that represents the result of running a test case. The result can either be a failure that contains a message regarding the failure, or a TestSuccess that simply indicates that the test passed:

case class TestCase(description: TestDescription, run: () => TestResult)
case class TestDescription(name...