Hands-On Design Patterns with Kotlin

Sealed, not enumerated

Coming from Java, you may be tempted to overload your enum with functionality:

// Java codeenum PizzaOrderStatus {    ORDER_RECEIVED,     PIZZA_BEING_MADE,     OUT_FOR_DELIVERY,     COMPLETED;    public PizzaOrderStatus nextStatus() {        switch (this) {            case ORDER_RECEIVED: return PIZZA_BEING_MADE;            case PIZZA_BEING_MADE: return OUT_FOR_DELIVERY;            case OUT_FOR_DELIVERY: return COMPLETED;            case COMPLETED:return COMPLETED;        }    }}

Instead, you can use the sealed class:

sealed class PizzaOrderStatus(protected val orderId: Int) {    abstract fun nextStatus() : PizzaOrderStatus    class OrderReceived(orderId: Int) : PizzaOrderStatus(orderId) {        override fun nextStatus(): PizzaOrderStatus {            return PizzaBeingMade(orderId)        }    }    class PizzaBeingMade(orderId: ...