RxSwift + State Machine, inspired by Redux and Elm.
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inamiy Merge pull request #19 from haritowa/swift/4.0
Fix double subscription bug
Latest commit 7bbcb35 Mar 13, 2018

README.md

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`.

License

MIT