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
```mermaid
stateDiagram-v2
stopped --> playing : play
playing --> paused : pause
playing --> stopped : stop
paused --> playing : play
paused --> stopped : stop
```
- 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.
Add the following dependency to your Package.swift file:
.dependencies = [
.package(url: "https://github.com/marcy731/StateMachine.git", from: "0.2.0")
]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: playingThis project is licensed under the MIT License. See the LICENSE file for details.