Prototype: making EventSource a Connectable<M, E>

Author: dalef84

MobiusCore/Source/Mobius.swift

@@ -74,7 +74,7 @@ public enum Mobius {
         return Builder(
             update: update,
             effectHandler: effectHandler,
-            eventSource: AnyEventSource({ _ in AnonymousDisposable(disposer: {}) }),
+            eventSource: AnyConnectable { _ in .init(acceptClosure: { _ in }, disposeClosure: {}) },
             eventConsumerTransformer: { $0 },
             logger: AnyMobiusLogger(NoopLogger())
         )
@@ -104,14 +104,14 @@ public enum Mobius {
     public struct Builder<Model, Event, Effect> {
         private let update: Update<Model, Event, Effect>
         private let effectHandler: AnyConnectable<Effect, Event>
-        private let eventSource: AnyEventSource<Event>
+        private let eventSource: AnyConnectable<Model, Event>
         private let logger: AnyMobiusLogger<Model, Event, Effect>
         private let eventConsumerTransformer: ConsumerTransformer<Event>
 
         fileprivate init<EffectHandler: Connectable>(
             update: Update<Model, Event, Effect>,
             effectHandler: EffectHandler,
-            eventSource: AnyEventSource<Event>,
+            eventSource: AnyConnectable<Model, Event>,
             eventConsumerTransformer: @escaping ConsumerTransformer<Event>,
             logger: AnyMobiusLogger<Model, Event, Effect>
         ) where EffectHandler.Input == Effect, EffectHandler.Output == Event {
@@ -140,7 +140,35 @@ public enum Mobius {
             return Builder(
                 update: update,
                 effectHandler: effectHandler,
-                eventSource: AnyEventSource(eventSource),
+                eventSource: AnyConnectable { consumer in
+                    var disposable: Disposable? = eventSource.subscribe(consumer: consumer)
+                    return .init(acceptClosure: { _ in // EventSource ignores the Model (value)
+                    }, disposeClosure: {
+                        disposable?.dispose()
+                        disposable = nil
+                    })
+                },
+                eventConsumerTransformer: eventConsumerTransformer,
+                logger: logger
+            )
+        }
+
+        /// TODO
+   /*
+   @return a new {@link Builder} with the supplied {@link Connectable<M,E>}, and the same values
+    as the current one for the other fields. NOTE: Invoking this method will replace the
+    current event source with the supplied one. If a loop has a {@link Connectable<M,E>} as
+    its event source, it will connect to it and will invoke the {@link Connection<M>} accept
+    method every time the model changes. This allows us to conditionally subscribe to
+    different sources based on the current state. If you provide a regular {@link
+    EventSource<E>}, it will be wrapped in a {@link Connectable} and that implementation will
+    subscribe to that event source only once when the loop is initialized.
+        */
+        public func withEventSource<Source: Connectable>(_ eventSource: Source) -> Builder where Source.Input == Model, Source.Output == Event {
+            return Builder(
+                update: update,
+                effectHandler: effectHandler,
+                eventSource: AnyConnectable(eventSource),
                 eventConsumerTransformer: eventConsumerTransformer,
                 logger: logger
             )

MobiusCore/Source/MobiusLoop.swift

@@ -25,6 +25,7 @@ public final class MobiusLoop<Model, Event, Effect>: Disposable {
     private var workBag: WorkBag
 
     private var effectConnection: Connection<Effect>! = nil
+    private var eventSourceConnection: Connection<Model>! = nil
     private var consumeEvent: Consumer<Event>! = nil
     private let modelPublisher: ConnectablePublisher<Model>
 
@@ -35,7 +36,7 @@ public final class MobiusLoop<Model, Event, Effect>: Disposable {
     init(
         model: Model,
         update: Update<Model, Event, Effect>,
-        eventSource: AnyEventSource<Event>,
+        eventSource: AnyConnectable<Model, Event>,
         eventConsumerTransformer: ConsumerTransformer<Event>,
         effectHandler: AnyConnectable<Effect, Event>,
         effects: [Effect],
@@ -72,12 +73,14 @@ public final class MobiusLoop<Model, Event, Effect>: Disposable {
 
         // These must be set up after consumeEvent, which refers to self; that’s why they need to be IUOs.
         self.effectConnection = effectHandler.connect(consumeEvent)
-        let eventSourceDisposable = eventSource.subscribe(consumer: consumeEvent)
+        self.eventSourceConnection = eventSource.connect { event in
+            consumeEvent(event) // TODO what about the model??
+        }
 
         self.disposable = CompositeDisposable(disposables: [
             effectConnection,
             modelPublisher,
-            eventSourceDisposable,
+            eventSourceConnection,
         ])
 
         // Prime the modelPublisher, and queue up any initial effects.
@@ -154,6 +157,7 @@ public final class MobiusLoop<Model, Event, Effect>: Disposable {
     private func processNext(_ next: Next<Model, Effect>) {
         if let newModel = next.model {
             model = newModel
+            eventSourceConnection.accept(model)
             modelPublisher.post(model)
         }
 

MobiusCore/Test/MobiusControllerTests.swift

@@ -28,8 +28,11 @@ class MobiusControllerTests: QuickSpec {
     override func spec() {
         describe("MobiusController") {
             var controller: MobiusController<String, String, String>!
+            var updateFunction: Update<String, String, String>!
+            var initiate: Initiate<String, String>!
             var view: RecordingTestConnectable!
             var eventSource: TestEventSource<String>!
+            var connectableEventSource: TestConnectableEventSource<String, String>!
             var effectHandler: RecordingTestConnectable!
             var activateInitiator: Bool!
 
@@ -42,13 +45,13 @@ class MobiusControllerTests: QuickSpec {
                 view = RecordingTestConnectable(expectedQueue: self.viewQueue)
                 let loopQueue = self.loopQueue
 
-                let updateFunction = Update<String, String, String> { model, event in
+                updateFunction = .init { model, event in
                     dispatchPrecondition(condition: .onQueue(loopQueue))
                     return .next("\(model)-\(event)")
                 }
 
                 activateInitiator = false
-                let initiate: Initiate<String, String> = { model in
+                initiate = .init { model in
                     if activateInitiator {
                         return First(model: "\(model)-init", effects: ["initEffect"])
                     } else {
@@ -57,6 +60,7 @@ class MobiusControllerTests: QuickSpec {
                 }
 
                 eventSource = TestEventSource()
+
                 effectHandler = RecordingTestConnectable()
 
                 controller = Mobius.loop(update: updateFunction, effectHandler: effectHandler)
@@ -356,6 +360,35 @@ class MobiusControllerTests: QuickSpec {
                 }
             }
 
+            describe("dispatching events using connectable") {
+                beforeEach {
+                    // Rebuild the controller but use the Connectable instead of plain EventSource
+                    connectableEventSource = .init()
+
+                    controller = Mobius.loop(update: updateFunction, effectHandler: effectHandler)
+                        .withEventSource(connectableEventSource)
+                        .makeController(
+                            from: "S",
+                            initiate: initiate,
+                            loopQueue: self.loopQueue,
+                            viewQueue: self.viewQueue
+                        )
+                    controller.connectView(view)
+                    controller.start()
+                }
+
+                it("should dispatch events from the event source") {
+                    connectableEventSource.dispatch("event source event")
+
+                    expect(view.recorder.items).toEventually(equal(["S", "S-event source event"]))
+                }
+
+                it("should receive models from the event source") {
+                    view.dispatch("new model")
+                    expect(connectableEventSource.models).toEventually(equal(["S", "S-new model"]))
+                }
+            }
+
             describe("deallocating") {
                 var modelObserver: MockConsumerConnectable!
                 var effectObserver: MockConnectable!

MobiusCore/Test/TestingUtil.swift

@@ -193,3 +193,60 @@ class TestEventSource<Event>: EventSource {
         }
     }
 }
+
+class TestConnectableEventSource<Model, Event>: Connectable {
+    typealias Input = Model
+    typealias Output = Event
+
+    enum Connection {
+        case disposed
+        case active(Consumer<Event>)
+    }
+    private(set) var connections: [Connection] = []
+    private(set) var models: [Model] = []
+    private var pendingEvent: Event?
+
+    var activeConnections: [Consumer<Event>] {
+        return connections.compactMap {
+            switch $0 {
+            case .disposed:
+                return nil
+            case .active(let consumer):
+                return consumer
+            }
+        }
+    }
+
+    var allDisposed: Bool {
+        return activeConnections.isEmpty
+    }
+
+    func connect(_ consumer: @escaping MobiusCore.Consumer<Event>) -> MobiusCore.Connection<Model> {
+        let index = connections.count
+        connections.append(.active(consumer))
+
+        if let event = pendingEvent {
+            consumer(event)
+            pendingEvent = nil
+        }
+
+        return .init(
+            acceptClosure: { [weak self] model in
+                self?.models.append(model)
+            }, disposeClosure: { [weak self] in
+                self?.connections[index] = .disposed
+            }
+        )
+    }
+
+    // Set an event to dispatch immediately when subscribed
+    func dispatchOnSubscribe(_ event: Event) {
+        pendingEvent = event
+    }
+
+    func dispatch(_ event: Event) {
+        activeConnections.forEach {
+            $0(event)
+        }
+    }
+}