Given you have an API for an specific situation th...

# codingconventions

[gabrielfv]

Given you have an API for an specific situation that is supposed to be used somewhat like that:

interface StateMachine<S> {
    fun updateState(state: S)
}

Where S needs to be a class that is able to represent the state of an UI element. What would you set as the upper-bound of S?

// 1
interface StateMachine<S : Any>

or

// 2
interface StateMachine<S : State>

// where
interface State  // There is no specific contract expected

[Czar]

I would also make State a sealed class instead of an interface, if possible. In fact why not make the StateMachine itself a sealed class hierarchy and get rid of the generic parameter altogether?
E.g.

sealed class Door
class OpenDoor : Door()
class ClosedDoor : Door()
// instead of
interface DoorState
class Closed : DoorState
class Open : DoorState
class Door<DoorState>

//this would make use of the state machine more type safe, and no dealing with type erasure.

[gabrielfv]

Because that's completely off the point. Something I forgot to mention, StateMachine is an API to be implemented in multiple different contexts (thus why it's an interface, not a class). So the concrete usage would be something like you mentioned:

class MyStateMachine : StateMachine<Door> {
    // ...
}

sealed class Door [: State] {
    class OpenDoor : Door()
}

[Czar]

I see, that's why I have "if possible" in my answer, not knowing the full context I was just making a generic suggestion 🙂