typeclass

typeclass.scala

// Inspiration : https://alvinalexander.com/scala/fp-book/type-classes-101-introduction
// Purpose : Adhoc polymorphsim

// Define some types
case class Dog(name: String, breed: String)

// Define the type class
trait Animal[A] {
    def sound(a: A): Unit
}

// Define a callable interface object
object AnimalInstances {
  def makeSound[A](a: A)(implicit animal: Animal[A]): Unit = {
        animal.sound(a)
  }
}

// Define a type class instance, these are defined adhoc where we want
implicit val dogVal = new Animal[Dog] {
  def sound(dog: Dog): Unit = {
      println(s"I'm a Dog, my name is ${dog.name} and my breed is ${dog.breed}")
  }
}

// Use the type class in code. 
val brendansdog = new Dog("Arnie", "Scottish Terrier")
AnimalInstances.makeSound(brendansdog)