1. We expect the reader to be comfortable with structuring and implementing simple programs in Scala and familiar with SBT and REPL. No previous knowledge of reactive programming, Akka, or microservices is required, but familiarity with the underlying concepts would be beneficial.
2. To work with the code examples in this book, Java 1.8+ and SBT 1.2+ need to be installed. The installation of Git is recommended to simplify checking out the source code from GitHub. For those readers who don't have the prerequisite software ready, we provide installation instructions for Java and SBT in Appendix A.

You can download the example code files for this book from your account at www.packt.com. If you purchased this book elsewhere, you can visit www.packt.com/support and register to have the files emailed directly to you.

You can download the code files by following these steps:

1. Log in or register at www.packt.com.
2. Select the SUPPORT tab.
3. Click on Code Downloads & Errata.
4. Enter the name of the book in the Search box and follow the onscreen instructions.

Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of:

• WinRAR/7-Zip for Windows
• Zipeg/iZip/UnRarX for Mac
• 7-Zip/PeaZip for Linux

The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Learn-Scala-Programming. In case there's an update to the code, it will be updated on the existing GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: http://www.packtpub.com/sites/default/files/downloads/9781788836302_ColorImages.pdf.

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "In Scala 2.13, StringOps has been extended with option-returning methods for string literals parsing. Supported types include all numeric types and Boolean."

A block of code is set as follows:

object UserDb {
  def getById(id: Long): User = ???
  def update(u: User): User = ???
  def save(u: User): Boolean = ???
}

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

scala> val user = User("John", "Doe", "[email protected]")
user: User = User(John,Doe,[email protected])
scala> naiveToJsonString(user)
res1: String = { "name": "John", "surname": "Doe", "email": "[email protected]" }

Any command-line input or output is written as follows:

take
-S--c--a--l--a-- --2--.--1--3-
take
Lazy view constructed: -S-S-c-C-a-A-l-L-a-A- - 
Lazy view forced: -S--c--a--l--a-- -List(S, C, A, L, A, )
Strict: List(S, C, A, L, A, )

Bold: Indicates a new term, an important word, or words that you see on screen.