StateMachine

StateMachine is a generic state machine library written in Swift. It offers an easy way to manage states, events, transitions, and side effects, aiding in writing robust code.

stateDiagram-v2
    stopped --> playing : play

    playing --> paused : pause
    playing --> stopped : stop

    paused --> playing : play
    paused --> stopped : stop

Loading

```mermaid
stateDiagram-v2
    stopped --> playing : play

    playing --> paused : pause
    playing --> stopped : stop

    paused --> playing : play
    paused --> stopped : stop
```

Features

• Type-Safe: States and events are strictly typed through protocols.
• Side Effect Management: Set optional side effects during transitions.
• Error Handling: Throws an error if an undefined transition is attempted.

Installation

Swift Package Manager

Add the following dependency to your Package.swift file:

.dependencies = [
    .package(url: "https://github.com/marcy731/StateMachine.git", from: "0.2.0")
]

Usage

Here's a basic example:

import StateMachine

enum State: StateHashable {
    case stopped, playing, paused
}

enum Event: EventHashable {
    case play, pause, stop
}

enum SideEffect: SideEffectHashable {
    case logPlay, logPause, logStop
}

let transitions: [Transition<State, Event, SideEffect>] = [
    // from State.stopped
    .init(from: .stopped, to: .playing, on: .play, with: .logPlay),

    // from State.playing
    .init(from: .playing, to: .paused, on: .pause, with: .logPause),
    .init(from: .playing, to: .stopped, on: .stop, with: .logStop),

    // from State.
    .init(from: .paused, to: .playing, on: .play, with: .logPlay),
    .init(from: .paused, to: .stopped, on: .stop, with: .logStop),
]

let stateMachine = StateMachine(initialState: .stopped, transitions: transitions) { result in
    if case .failure(let error) = result, case .undefinedTransition = error {
        assertionFailure(error.description)
    }

    if case .success(let transition) = result, let sideEffect = transition.sideEffect {
        switch sideEffect {
        case .logPlay, .logPause, .logStop:
            print(transition.description)
        }
    }
}

stateMachine.apply(.play)
print(stateMachine.state) // Outputs: playing

License

This project is licensed under the MIT License. See the LICENSE file for details.