Polymorphism in Scala: Unifying Flexibility and Reusability | CodeSignal Learn

Polymorphism in Scala: Unifying Flexibility and Reusability | CodeSignal Learn

Enough theory—let's witness polymorphism flex its muscles in Scala! We'll explore how to implement it using abstract classes and method overriding.

Scala

// Define an abstract class Person with name and age attributes
abstract class Person(val name: String, val age: Int):
  def display(): Unit =
    println(s"Name: $name, Age: $age")

// Define a derived class Student with a major attribute
class Student(name: String, age: Int, val major: String) extends Person(name, age):
  override def display(): Unit =
    super.display()
    println(s"Major: $major")

// Define a derived class Teacher with a subject attribute
class Teacher(name: String, age: Int, val subject: String) extends Person(name, age):
  override def display(): Unit =
    super.display()
    println(s"Subject: $subject")

@main def main(): Unit =
  // Create a list of Person references encompassing Student and Teacher objects
  val people: List[Person] = List(
    Student("Alice", 30, "Computer Science"),
    Teacher("Bob", 25, "Mathematics")
  )

  // Use polymorphism to call display on each object in the list
  people.foreach(_.display())

In this code snippet, the display method in Student and Teacher classes overrides the base class method defined in Person. When we call display on each element in the people list, Scala dynamically invokes the appropriate method depending on the object's actual class: the super.display() call ensures that the base class method is executed first, and then the specific behavior of the subclass is added on top of that. The people list holds references of type Person, but the actual objects are instances of Student and Teacher. This is polymorphism in action!

When you run this code, you'll see that each object's specific display method is executed:

text

Name: Alice, Age: 30
Major: Computer Science
Name: Bob, Age: 25
Subject: Mathematics