Scala Type Classes

A type class is a group of types that enable a predetermined range of habits in the framework of the Scala programming language. For instance, this may be the type group that exposes a special integer identifier. Scala acquires ad hoc polymorphism due to the strong and adaptable idea of the type classes. Although the language does not regard them as first-class citizens, various constructed methods enable to construct them in Scala. This means that these are not always easy to notice in the program, and there could also be a misunderstanding on the “appropriate” method to writing them. The concept of the type classes, how they operate, and the procedure for programming them in Scala are all outlined in this new article.

Before creating any program of any language, you need to set the environment for that language in your system first. As we want to do coding in the Scala language, we have to make sure that it’s already been configured at our end. If it’s not configured yet, you have to configure it using the install instruction of Ubuntu 20.04 at the console application. After the complete and successful configuration, write “scala” at your console shell and you will be shown with a scala shell along with its installed version.

Example 1:
Syntactic sugar is frequently used in the type class implementations, which further obscures the nature of the entity that we are working with. Let’s begin by taking the modest steps to set up and comprehend a type of class. This is accomplished by the use of a trait and a handful of inferred objects of that characteristic. Any sealed data type can have additional behavior added to it without the use of sub-typing because of the abstract type classes parametric types. So, within the Scala shell, we created a trait “Test[A]” that encapsulates a “test” function. The function definition of the “test” function contains a variable “x” and a type “A” in it to be used in the future. The String keyword along with it is used to show that this function displays a type of object “A” which can create a text representation of it in running these 2 lines of code on the Scala shell. We created the “Test” trait successfully.

It’s time to create some child class extending a parent class Test that contains a particular type [A] for an object created in the previous illustration which is Test. For an instance, we suggest that you use the Int type for the object “Test” for now to extend the main Test class in the child class “TestInt”. We create a function definition for the “test” function within this child class having the same function as we have in the main Test class. This time, we specify the type of parameter. This function uses as “Int” and adds a string that uses this variable “x” in it for displaying. The “TestInt” class is defined successfully.

After this, we use another function definition “toHtml” that works on a random type “A” as we specified. This function uses the variable “x” of “A” type and the object “Test” of the main Test class in its two parameters. Utilizing the “test” function from the object “Test” class, it uses a String keyword to create an HTML string. The string from the “TestInt” class is used here in place of “testA.test(x)”.

On running the “toHtml” function with an Integer value and a TestInt arbitrary object, it will likely display a full string containing an HTML type format. The output is displayed on the console screen just like “<p> Value: 13 </p>”.


Example 2:
The previous example is all about using the type classes in a Scala shell to elaborate it in a basic way. Now, we use the Scala file to create the Scala program and run it on the console. For this, we create a new Scala file by making use of the “touch” query as displayed. The listed contents have a test.scala file as well. Open this file in a text editor first.

We start our Scala code by the creation of an object “test” to make it utilized for code execution in the coming future. This code contains the main() function definition that holds the rest of the code in it. It starts with the trait named “Print” that holds a type “A”. This “A” can be of any type. It holds the function definition for a function named “display” that takes the “x” value of type “A” from the user. After the trait type class, we define another function “display” that inherits the properties of a trait class “Print” within it. It uses two parameters, the same variable “x” of type A and an implicit type object “o” from the Print[A] main type class. Along with this, the implicit object is used to call the display function of the trait “Print” by passing it a variable “x”. After this, we use the “display” function in it, taking the integer type variable value to be passed to a string that is already listed. In the end, the println() function statement calls the “display” function with value 3.

Upon the compilation and execution of this code file, we got the variable “x = 13” displayed along with the type class “Int” at the console.


This article briefly explained the use of the type classes in Scala as a comparison with Java programming. Although there isn’t a specific syntax in Scala to represent a type class, the very same feature may be accomplished using the language’s built-in features. Because of this, it might be a bit challenging for beginners to identify a type of class in code. But, with our codes mentioned in the given examples, you will be able to learn it fully.

About the author

Saeed Raza

Hello geeks! I am here to guide you about your tech-related issues. My expertise revolves around Linux, Databases & Programming. Additionally, I am practicing law in Pakistan. Cheers to all of you.