RxAutomaton
RxSwift port of ReactiveAutomaton (State Machine).
Terminology
Whenever the word "signal" or "(signal) producer" appears (derived from ReactiveCocoa), they mean "hot-observable" and "cold-observable".
Example
(Demo app is bundled in the project)
To make a state transition diagram like above with additional effects, follow these steps:
// 1. Define `State`s and `Input`s.
enum State {
case loggedOut, loggingIn, loggedIn, loggingOut
}
enum Input {
case login, loginOK, logout, logoutOK
case forceLogout
}
// Additional effects (`Observable`s) while state-transitioning.
// (NOTE: Use `Observable.empty()` for no effect)
let loginOKProducer = /* show UI, setup DB, request APIs, ..., and send `Input.loginOK` */
let logoutOKProducer = /* show UI, clear cache, cancel APIs, ..., and send `Input.logoutOK` */
let forcelogoutOKProducer = /* do something more special, ..., and send `Input.logoutOK` */
let canForceLogout: State -> Bool = [.loggingIn, .loggedIn].contains
// 2. Setup state-transition mappings.
let mappings: [Automaton<State, Input>.EffectMapping] = [
/* Input | fromState => toState | Effect */
/* ----------------------------------------------------------------*/
.login | .loggedOut => .loggingIn | loginOKProducer,
.loginOK | .loggingIn => .loggedIn | .empty(),
.logout | .loggedIn => .loggingOut | logoutOKProducer,
.logoutOK | .loggingOut => .loggedOut | .empty(),
.forceLogout | canForceLogout => .loggingOut | forceLogoutOKProducer
]
// 3. Prepare input pipe for sending `Input` to `Automaton`.
let (inputSignal, inputObserver) = Observable<Input>.pipe()
// 4. Setup `Automaton`.
let automaton = Automaton(
state: .loggedOut,
input: inputSignal,
mapping: reduce(mappings), // combine mappings using `reduce` helper
strategy: .latest // NOTE: `.latest` cancels previous running effect
)
// Observe state-transition replies (`.success` or `.failure`).
automaton.replies.subscribe(next: { reply in
print("received reply = \(reply)")
})
// Observe current state changes.
automaton.state.asObservable().subscribe(next: { state in
print("current state = \(state)")
})And let's test!
let send = inputObserver.onNext
expect(automaton.state.value) == .loggedIn // already logged in
send(Input.logout)
expect(automaton.state.value) == .loggingOut // logging out...
// `logoutOKProducer` will automatically send `Input.logoutOK` later
// and transit to `State.loggedOut`.
expect(automaton.state.value) == .loggedOut // already logged out
send(Input.login)
expect(automaton.state.value) == .loggingIn // logging in...
// `loginOKProducer` will automatically send `Input.loginOK` later
// and transit to `State.loggedIn`.
// 👨🏽 < But wait, there's more!
// Let's send `Input.forceLogout` immediately after `State.loggingIn`.
send(Input.forceLogout) // 💥💣💥
expect(automaton.state.value) == .loggingOut // logging out...
// `forcelogoutOKProducer` will automatically send `Input.logoutOK` later
// and transit to `State.loggedOut`.