Code for Spacecat's Essential Scala

Copyright 2022 Spacecat Ltd.

This repository contains exercises and solutions for Spacecat's Essential Scala training course.

If you want to discuss the content or exercises with the authors, contact using the contact details on our web site.

Using the Source Code

This repository contains two branches: one for exercises and one for solutions. The directory structure is the same in each branch.

You will need to have Git and Java and an internet connection to run the exercises. Other dependencies are either included with the repository or downloaded on demand during compilation.

Each exercise is in its own SBT sub-project so it can be compiled and run separately from the rest of the code. You can see a list of projects by typing projects at the SBT prompt:

sbt:exercises> projects
[info] In file:/.../essential-scala-code/
[info] 	   exercise1
[info] 	   exercise2
[info] 	   exercise3
[info] 	   etc...

The projects are as follows:

• helloworld is used to verify the setup instructions below;
• sandbox is your area to test things out;
• each numbered exercise is one of the exercises in the course;
• exercises is an "aggregate" project that comprises all of the above.

Useful Commands

You can run a command on a specific project by typing projectName/command, where projectName is one of the names above:

• projectName/compile -- compile an exercise;
• projectName/run -- run an exercise (recompiles if necessary);
• projectName/test -- run the tests for an exercise (recompiles if necessary).

Additionally, the following commands apply to all projects in the buid:

• to compile all the sub-projects at once, type compile;
• to run all the unit tests, type test.

Running Commands in Watch Mode

Prefix any of the commands with a tilde (~) to run it in watch mode. The command will run once immediately then wait for you to save a file before running again. You can cancel watch mode with Ctrl+C.

Editors and IDEs

If you don't have a preference for a Scala editor or IDE, we recommend using Visual Studio Code and a Linux or OS X terminal. See the instructions below to get started.

If you want to use IntelliJ IDEA with the IntelliJ Scala Plugin, follow the instructions for opening a project in their online documentation.

Getting started on Linux or macOS

1. To run these exercises, you need a Java 8 compatible JDK. If you don't have this already, you can download and install one from Oracle Java SE Development Kit 8+ or OpenJDK 8+.

2. Clone this repository to a directory on your hard drive, e.g. ~/essential-scala-code:

   git clone https://github.com/underscoreio/essential-scala-code.git

3. Change to the root directory in the repository:

   cd essential-scala-code

4. Run the sbt.sh script. You may have to wait while SBT downloads various dependencies:

   ./sbt.sh
   # Lots of output here...
   # The first run will take a while...
   
   sbt:exercises>

5. Type helloworld/run at the SBT prompt. You may have to wait while SBT downloads various dependencies. If you see the message "Hello world!", you're ready to go!

   sbt:exercises> helloworld/run
   [info] compiling 1 Scala source ...
   [info] running HelloWorld
   
   Hello World!
   
   [success] Total time: 3 s
   

Getting Started on Windows

You will need to have installed Git and Java (we recommend Oracle's Java 8 SDK). Complete the following steps outlined in Chapter 1 in the section entitled "Setting up SBT for This Book":

1. To run these exercises, you need a Java 8 compatible JDK on your machine. If you don't have this already, you can download and install one from Oracle Java SE Development Kit 8+ or OpenJDK 8+.

2. Clone this repository to a directory on your hard drive, e.g. C:\essential-scala-code:

   git clone https://github.com/underscoreio/essential-scala-code.git C:\essential-scala-code
   

3. Change to the root directory in the repository:

   cd\essential-scala-code
   

4. Run the sbt.bat script. You may have to wait while SBT downloads various dependencies:

   sbt.bat
   # Lots of output here...
   # The first run will take a while...
   
   sbt:exercises>
   

5. Type helloworld/run at the SBT prompt. You may have to wait while SBT downloads various dependencies. If you see the message "Hello world!", you're ready to go!

   sbt:exercises> helloworld/run
   [info] compiling 1 Scala source ...
   [info] running HelloWorld
   
   Hello World!
   
   [success] Total time: 3 s