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Introduction

SBT (Simple Build Tool) is a popular build tool for Scala projects. It is used to compile, run, and test Scala code, manage dependencies, and automate various tasks in the development lifecycle. SBT is highly customizable and integrates well with other tools and libraries in the Scala ecosystem.

Key Concepts

Build Definition

Build.sbt: The main build definition file where you specify project settings, dependencies, and tasks.
Project Directory: Contains additional configuration files and project-specific settings.

Dependencies

Library Dependencies: External libraries that your project depends on.
Resolvers: Repositories where SBT looks for dependencies.

Tasks and Commands

Tasks: Actions that SBT can perform, such as compiling code or running tests.
Commands: Instructions you give to SBT to execute tasks.

Setting Up SBT

Installation

Download and Install SBT:
- Visit the SBT download page and follow the instructions for your operating system.
- Verify the installation by running sbt sbtVersion in your terminal.

Creating a New Project

Create a Project Directory:

mkdir my-scala-project
cd my-scala-project

Initialize SBT:
```
sbt new scala/scala-seed.g8
```

Project Structure:

my-scala-project/
├── build.sbt
├── project/
├── src/
│   ├── main/
│   │   └── scala/
│   └── test/
│       └── scala/
└── target/

Writing the Build Definition

Basic build.sbt File

name := "MyScalaProject"

version := "0.1.0"

scalaVersion := "2.13.6"

libraryDependencies += "org.scalatest" %% "scalatest" % "3.2.9" % Test

Explanation

name: The name of your project.
version: The version of your project.
scalaVersion: The version of Scala to use.
libraryDependencies: External libraries your project depends on. In this case, ScalaTest for testing.

Common SBT Commands

Running SBT

Start SBT Shell:
```
sbt
```

Compilation

Compile the Project:
```
compile
```

Running the Project

Run the Main Class:
```
run
```

Testing

Run Tests:
```
test
```

Dependency Management

Update Dependencies:
```
update
```

Practical Example

Example Project: Hello World

Create a New Project:
```
sbt new scala/scala-seed.g8
```

Edit build.sbt:

name := "HelloWorld"

version := "0.1.0"

scalaVersion := "2.13.6"

Create Main Class:
- Create a file src/main/scala/HelloWorld.scala:
```
object HelloWorld extends App {
  println("Hello, World!")
}
```
Run the Project:
```
sbt run
```

Output

[info] running HelloWorld 
Hello, World!

Exercises

Exercise 1: Adding a Dependency

Task: Add the json4s library to your project.

Solution:

Edit build.sbt:

libraryDependencies += "org.json4s" %% "json4s-native" % "3.6.11"

Exercise 2: Creating a Test

Task: Write a test for the HelloWorld object.

Solution:

Add ScalaTest dependency in build.sbt:

libraryDependencies += "org.scalatest" %% "scalatest" % "3.2.9" % Test

Create a test file src/test/scala/HelloWorldTest.scala:

import org.scalatest.flatspec.AnyFlatSpec

class HelloWorldTest extends AnyFlatSpec {
  "HelloWorld" should "print Hello, World!" in {
    assert(HelloWorld.main(Array()) == "Hello, World!")
  }
}

Conclusion

In this section, you learned about SBT, its key concepts, and how to set up and manage a Scala project using SBT. You also practiced adding dependencies and writing tests. Understanding SBT is crucial for efficient Scala development, and mastering it will significantly enhance your productivity.

SBT (Scala Build Tool)