Forked from nixzhu/StateMachine-TransitionFunction.swift
Created
February 25, 2020 14:27
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| struct StateMachine<State, Action> { | |
| private(set) var state: State | |
| private let transition: (State, Action) -> State? | |
| init(startState: State, transition: @escaping (State, Action) -> State?) { | |
| self.state = startState | |
| self.transition = transition | |
| } | |
| mutating func apply(action: Action) -> Bool { | |
| if let nextState = transition(state, action) { | |
| state = nextState | |
| return true | |
| } | |
| return false | |
| } | |
| } | |
| struct Light { | |
| enum State { | |
| case on, off, broken | |
| } | |
| enum Action { | |
| case turn, cut | |
| } | |
| private var sm = StateMachine<State, Action>(startState: .off) { state, action -> State? in | |
| switch (state, action) { | |
| case (.off, .turn): return .on | |
| case (.on, .turn): return .off | |
| case (_, .cut): return .broken | |
| default: return nil | |
| } | |
| } | |
| var state: State { | |
| return sm.state | |
| } | |
| @discardableResult | |
| mutating func apply(action: Action) -> Bool { | |
| return sm.apply(action: action) | |
| } | |
| } | |
| var light = Light() | |
| light.apply(action: .turn) | |
| light.state | |
| light.apply(action: .turn) | |
| light.state | |
| light.apply(action: .turn) | |
| light.state | |
| light.apply(action: .cut) | |
| light.state | |
| light.apply(action: .cut) | |
| light.state | |
| light.apply(action: .turn) | |
| light.state |
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