StateKit

Type-safe async state machine with built-in logging and SwiftUI bindings

Requirements

• Swift >= 6.0
• macOS 13+ / iOS 16+ / tvOS 16+ / watchOS 9+

Installation

Add to your Package.swift:

dependencies: [
    .package(url: "https://github.com/philiprehberger/swift-state-kit.git", from: "0.1.0")
]

Then add "StateKit" to your target dependencies:

.target(name: "YourTarget", dependencies: [
    .product(name: "StateKit", package: "swift-state-kit")
])

Usage

import StateKit

// Define states and events
enum OrderState: Hashable, Sendable {
    case pending, confirmed, shipped, delivered
}

enum OrderEvent: Hashable, Sendable {
    case confirm, ship, deliver
}

// Define transitions
let machine = StateMachine(
    initial: OrderState.pending,
    transitions: [
        Transition(from: .pending, on: .confirm, to: .confirmed),
        Transition(from: .confirmed, on: .ship, to: .shipped),
        Transition(from: .shipped, on: .deliver, to: .delivered)
    ]
)

let state = try await machine.send(.confirm)  // => .confirmed

Async Side Effects

Transition(from: .pending, on: .confirm, to: .confirmed) {
    try await sendConfirmationEmail()
}

Logging

let machine = StateMachine(
    initial: OrderState.pending,
    transitions: transitions,
    logger: .console
)
// Logs: "[StateKit] pending --confirm--> confirmed"

SwiftUI Integration

struct OrderView: View {
    @State private var machine = ObservableStateMachine(machine: orderMachine)

    var body: some View {
        VStack {
            Text("Status: \(machine.state)")
            Button("Confirm") { Task { try await machine.send(.confirm) } }
                .disabled(!await machine.canSend(.confirm))
        }
    }
}

API

StateMachine

Method	Description
init(initial:transitions:logger:)	Create a state machine with initial state and transitions
send(_:)	Send an event to trigger a transition
canSend(_:)	Check if an event is valid in the current state
onTransition(_:)	Register a callback for state changes
currentState	The current state

Transition

Property	Description
from	Source state
event	Triggering event
to	Destination state
sideEffect	Optional async closure executed during transition

ObservableStateMachine

Property/Method	Description
state	Current state (observable)
isTransitioning	Whether a transition is in progress
send(_:)	Send an event
canSend(_:)	Check if an event is valid

Development

swift build
swift test

Support

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License

MIT