Recording brought to you by American Express https://americanexpress.io/kotlin-jobs The talk explores using sealed classes to represent state via an event stream and how we can take filtered views of it while still maintaining the exhaustiveness of when. The talk would follow the concepts outlined in my post here: https://codeascraft.com/2018/04/12/sealed-classes-opened-my-mind/ Additionally it would explore how to use RxJava to emit these events and how to use when and filterIsInstance to react to them. There is a section on how Java's instanceof was often considered a poor practice and the (sometimes painful) indirection of polymorphic solutions like the visitor pattern. And finally how Kotlin makes all that pain go away. About Patrick Cousins: Been programming for nearly 20 years and I still love rediscovering that passion for new patterns and languages. Fan of corny jokes and seal puns.