Introduction to Sealed Classes and Interfaces

The Result interface and abstract class

Classes and interfaces in Kotlin are not only used to represent a set of operations or data. We can also use classes and inheritance to represent hierarchies through polymorphism. For instance, let’s say that we send a network request. As a result, we either successfully receive the requested data, or the request fails with some information about what went wrong. These two outcomes can be represented using two classes that implement an interface: