dependencies: [
    .package(url: "https://github.com/alexruperez/StateMachine.git")
]

class MyState: State {
    func isValidNext<S>(state type: S.Type) -> Bool where S : State {
        switch type {
        case is OneValidNextState.Type, is OtherValidNextState.Type:
            return true
        default:
            return false
        }
    }
}

class OneValidNextState: State {
    func isValidNext<S>(state type: S.Type) -> Bool where S : State {
        return type is OtherValidNextState.Type
    }

    func didEnter(from previous: State?) {
        // Your code here
    }
}

class OtherValidNextState: State {
    func isValidNext<S>(state type: S.Type) -> Bool where S : State {
        return false
    }

    func willExit(to next: State) {
        // Your code here
    }
}

let stateMachine = StateMachine([MyState(), OneValidNextState(), OtherValidNextState()])

stateMachine.enter(OneValidNextState.self)

stateMachine.enter(OtherValidNextState.self)

let subscriptionToken = stateMachine.subscribe { (previous, current) in
    // Your code here
}

stateMachine.unsubscribe(subscriptionToken)

stateMachine.unsubscribeAll()

if UIApplication.shared.stateMachine.current is ActiveApplicationState {
    // Your code here
}

let viewController = StatefulViewController()

if viewController.stateMachine.current is AppearingViewControllerState {
    // Your code here
}