SKB – Scala Sealed


This article is part of the Scala knowledge bits Series.

Periodically, I will publish new exercises so you can slowly build up knowledge about Scala.

It is designed to be done in a very short amount of time and learn a little bit each day, just to create a routine.

This episode will teach you about Scala sealed.

Hope you are going to enjoy it! It is designed for anyone to learn Scala from scratch and slowly learn, one Bit at a time.

After this Bit, I would love to hear your feedback in the comments down below.

Feel free to join the Discord server as well if you would like some help and support from the rest of our community.

What are we learning today?

Today we are going to learn about Scala sealed !

A simple new keyword today

It is not possible to illustrate its main function using Scastie, so if you would like to learn more you will have to read the description snippet below. I am sorry about that.

Time to try on the exercise on your own and scroll down for more information when you are done or if you are stuck.


Here is an exercise to complete today.

If I did my job well, you should be able to guess by yourself the solution based on what you previously learned and based on the clues.

But if you get stuck, scroll down to get more information.

The goal of the exercise is to replace the ??? by a piece of code so that the exercise compiles and that’s how you win! Good luck!

You can fill the exercise right in here:

Or, if it does not load, go on to Scastie (FLCt7eVzRmedD4gb40BpVQ).

More information about Scala sealed

In this exercise you will learn (or have learned, if you have already solved the puzzle) about Scala sealed.

We are reusing a lot of feature we saw in the past for this SKB. Everything should look familiar except the new keyword sealed

sealed is related to Object Oriented Programming and more specifically about inheritance.

The keyword sealed allows you to block inheritance if it is not within the same file. If you define a sealed trait or abstract class ( it works for both the exact same way ), you will only be able to extends this trait within this file.

This is the reason why it is hard to illustrate it within Scastie since everything is just one worksheet.

It is very useful when you want to describe something which have finite options. We are going to learn more about a very specific use case in the next SKB.

Feel free to go back to the exercise, modify the code to try out new things and get a better intuition for Scala sealed.


I hope you have learned something new or had fun during this Scala Knowledge Bit.

Please ask questions or post feedback in the comments below.

Feel free to try on the next Scala Knowledege Bit.

If you are curious about the previous Scala knowledge Bits, go check it out! 🙂

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