Scala Language Case Classes Case Class Basics


Example

In comparison to regular classes – case classes notation provides several benefits:

  • All constructor arguments are public and can be accessed on initialized objects (normally this is not the case, as demonstrated here):

    case class Dog1(age: Int)
    val x = Dog1(18)
    println(x.age) // 18 (success!)
    
    class Dog2(age: Int)
    val x = new Dog2(18)
    println(x.age) // Error: "value age is not a member of Dog2"
    
  • It provides an implementation for the following methods: toString, equals, hashCode (based on properties), copy, apply and unapply:

    case class Dog(age: Int)
    val d1 = Dog(10)
    val d2 = d1.copy(age = 15)
    
  • It provides a convenient mechanism for pattern matching:

    sealed trait Animal // `sealed` modifier allows inheritance within current build-unit only
    case class Dog(age: Int) extends Animal
    case class Cat(owner: String) extends Animal
    val x: Animal = Dog(18)
    x match {
        case Dog(x) => println(s"It's a $x years old dog.")
        case Cat(x) => println(s"This cat belongs to $x.")
    }