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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,24 @@ | ||
| import ReactiveSwift | ||
|
|
||
| extension Property { | ||
| public convenience init<Event>( | ||
| initial: Value, | ||
| reduce: @escaping (Value, Event) -> Value, | ||
| feedbacks: [Feedback<Value, Event>] | ||
| ) { | ||
| let state = MutableProperty(initial) | ||
| StateMachine.bootstrap(state: state.producer, | ||
| process: { [weak state] event in state?.modify { $0 = reduce($0, event) } }, | ||
| feedbacks: feedbacks, | ||
| lifetime: state.lifetime) | ||
| self.init(capturing: state) | ||
| } | ||
|
|
||
| public convenience init<Event>( | ||
| initial: Value, | ||
| reduce: @escaping (Value, Event) -> Value, | ||
| feedbacks: Feedback<Value, Event>... | ||
| ) { | ||
| self.init(initial: initial, reduce: reduce, feedbacks: feedbacks) | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| import ReactiveSwift | ||
| import Result | ||
|
|
||
| /// An `EventBuffer` manages the deferred processing of recursive events. | ||
| /// | ||
| /// When a given event is processed by a reducer, a new state would be computed together | ||
| /// with new feedbacks, which could potentially yield a new event synchronously. Since | ||
| /// the ReactiveSwift primitives do not support value recursion, the state machine would | ||
| /// need to specifically cater for this scenario so as to be synchronous by default. | ||
| private struct EventBuffer<Event> { | ||
| var isTransitioning: Bool | ||
| var events: ContiguousArray<Event> | ||
|
|
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| /// Dequeue the first event in the queue, or complete the transitioning if the queue | ||
| /// is empty. | ||
| mutating func completeOrDequeue() -> Event? { | ||
| assert(isTransitioning) | ||
| guard events.isEmpty | ||
| else { return events.removeFirst() } | ||
| isTransitioning = false | ||
| return nil | ||
| } | ||
| } | ||
|
|
||
| internal enum StateMachine { | ||
| internal static func bootstrap<State, Event>( | ||
| state: SignalProducer<State, NoError>, | ||
| process: @escaping (Event) -> Void, | ||
| feedbacks: [Feedback<State, Event>], | ||
| lifetime: Lifetime | ||
| ) { | ||
| // Treat initialisation as an implicit event, and buffer any event yielded during | ||
| // the initialisation. | ||
| let buffer = Atomic(EventBuffer<Event>(isTransitioning: true, events: [])) | ||
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| state.startWithSignal { state, interruptHandle in | ||
| lifetime += interruptHandle | ||
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| let events = feedbacks.map { feedback in | ||
| return feedback.events(ImmediateScheduler(), state) | ||
| } | ||
|
|
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| lifetime += Signal.merge(events) | ||
| .observeValues { event in | ||
| let shouldProceed: Bool = buffer.modify { buffer in | ||
| guard buffer.isTransitioning else { | ||
| // This event is not recursively sent during the processing | ||
| // of another event. | ||
| buffer.isTransitioning = true | ||
| return true | ||
| } | ||
|
|
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| buffer.events.append(event) | ||
| return false | ||
| } | ||
|
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| guard shouldProceed else { return } | ||
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| process(event) | ||
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| // Drain any event recursively yielded during `process(event)` above. | ||
| while let event = buffer.modify({ $0.completeOrDequeue() }) { | ||
| process(event) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // Drain any event yielded by the initial state. | ||
| while let event = buffer.modify({ $0.completeOrDequeue() }) { | ||
| process(event) | ||
| } | ||
| } | ||
| } |
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