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.
Table of Contents (19 chapters)

Using types to define domain constraints

We've already seen how simple types can be used to express domain constraints, as discussed in the Path-dependent types section. We implemented a lock that guaranteed at compile time that it is only possible to open and close it with the key created for this specific lock. We will conclude our study of type parameters and higher kinded types with two examples.

The first example will demonstrate an application of phantom types to create another version of the lock, which can guarantee the safety of state transitions at compile time without the use of inheritance.

The second example will show how self-recursive types can help to constrain possible subtyping.

Phantom types

The phantom...