To get the most out of this book

This book assumes that the reader is already familiar with Scala. We have provided examples for each chapter in projects using Maven and SBT. You should have some knowledge of either one of these tools and have it installed on your machine. You are also recommended to have a modern and up-to-date IDE installed on your computer, for example, IntelliJ. You are encouraged to open the actual projects, as the examples in this book focus on the design patterns and, in some cases, imports are omitted in favor of space.

The examples in the book were written and tested on a Unix-based operating system; however, they should also successfully compile and run on Windows.

Download the example code files

You can download the example code files for this book from your account at www.packtpub.com. If you purchased this book elsewhere, you can visit www.packtpub.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.packtpub.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/Scala-Design-Patterns-Second-Edition. 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!

Conventions used

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: "The base class is specified using extends and then all traits are added using the with keyword."

A block of code is set as follows:

class MultiplierIdentity {
  def identity: Int = 1
}

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

Error:(11, 8) object Clashing inherits conflicting members:
  method hello in trait A of type ()String and
  method hello in trait B of type ()String
(Note: this can be resolved by declaring an override in object Clashing.)
object Clashing extends A with B {
       ^

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

Result 1: 6
Result 2: 2
Result 3: 6
Result 4: 6
Result 5: 6
Result 6: 3

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

Warnings or important notes appear like this.

Tips and tricks appear like this.