Hands-On Object-Oriented Programming with Kotlin

Sealed classes

Every sealed class is tagged with the sealed keyword and is limited to a set of classes that can be declared inside the class body. Here is an example of a sealed class:

sealed class A(val number : Int) {     class B(n: Int) : A(n) {         fun display() { println("number = $number" ) }} class C(n: Int) : A(n){         fun square() { println("Square = "+ number * number) }     } }

class A is a sealed class and class B and class C are the classes that are inherited from class A. Before Kotlin 1.1, declaring a child class inside a sealed class was the only method of declaration. Now, however, we can extend the sealed class from outside the class body, as shown in the preceding example, where class C extends class A. Remember that both the sealed and ...