In this section, we will go over how to define and use traits in the Scala programming language.

If you recall from the Scala Introduction tutorial, Scala is both an Object Oriented and Functional programming language.

The examples in this chapter will start off with using traits in an Object Oriented fashion. As we progress throughout the chapter, we will show how to leverage traits in a pure Functional context.

Throughout the tutorials we will use the popular IntelliJ IDEA which we've setup in Chapter 1. I hope that by now you are more comfortable using IntelliJ. If not, feel free to review the previous tutorials from Chapter 1!

In this chapter, we will provide tutorials on the topics below. If none of these make any sense right now, that's OK :)

• Extend a single trait
• Extend multiple traits
• Using traits for dependency injection
• Dependency injection and the infamous Cake Pattern
• Mixin traits
• Traits as foundation to Functional Programming

So let's get started!

• Extend Trait
• Trait With Type Parameters
• Extend Multiple Traits
• Dependency Injection Using Traits
• Dependency Injection - Avoid Cake Pattern
• Traits, Companion Objects, Factory Pattern