Merge pull request #42 from CombineCommunity/feature/use-replay-subject

Feature/use replay subject

CHANGELOG.md

@@ -1,3 +1,7 @@
+**v0.4.0 - Bane**:
+
+- replace CurrentValueSubject by a ReplaySubject in System.stream
+
 **v0.3.0 - Tyranus**:
 
 - Feedback: introduce the "on:" keyword to explicitly declare the type of state that concerns the side effect

Examples/Examples.xcodeproj/project.pbxproj

@@ -7,9 +7,9 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		1A7057E7266167540070FD5D /* Feedbacks in Frameworks */ = {isa = PBXBuildFile; productRef = 1A7057E6266167540070FD5D /* Feedbacks */; };
+		1A7057E9266167950070FD5D /* FeedbacksTest in Frameworks */ = {isa = PBXBuildFile; productRef = 1A7057E8266167950070FD5D /* FeedbacksTest */; };
 		741C474025EC5CDB00F1231B /* Counter+TransitionsTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 741C473F25EC5CDB00F1231B /* Counter+TransitionsTests.swift */; };
-		741C475C25EC5DE100F1231B /* Feedbacks in Frameworks */ = {isa = PBXBuildFile; productRef = 741C475B25EC5DE100F1231B /* Feedbacks */; };
-		741C476625EC5E4C00F1231B /* FeedbacksTest in Frameworks */ = {isa = PBXBuildFile; productRef = 741C476525EC5E4C00F1231B /* FeedbacksTest */; };
 		742FEE2425B388DA00575CB2 /* GifList.swift in Sources */ = {isa = PBXBuildFile; fileRef = 742FEE2325B388DA00575CB2 /* GifList.swift */; };
 		742FEE2825B38B1A00575CB2 /* GifList+States.swift in Sources */ = {isa = PBXBuildFile; fileRef = 742FEE2725B38B1A00575CB2 /* GifList+States.swift */; };
 		742FEE2E25B38EEE00575CB2 /* GifOverview.swift in Sources */ = {isa = PBXBuildFile; fileRef = 742FEE2D25B38EEE00575CB2 /* GifOverview.swift */; };
@@ -66,6 +66,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		1A5E6478266166CA00F576A9 /* Feedbacks */ = {isa = PBXFileReference; lastKnownFileType = folder; name = Feedbacks; path = ..; sourceTree = "<group>"; };
 		741C473D25EC5CDB00F1231B /* ExamplesTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = ExamplesTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		741C473F25EC5CDB00F1231B /* Counter+TransitionsTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Counter+TransitionsTests.swift"; sourceTree = "<group>"; };
 		741C474125EC5CDB00F1231B /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
@@ -121,15 +122,15 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				741C476625EC5E4C00F1231B /* FeedbacksTest in Frameworks */,
+				1A7057E9266167950070FD5D /* FeedbacksTest in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
 		7471829D25AE7B0B0098E83E /* Frameworks */ = {
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				741C475C25EC5DE100F1231B /* Feedbacks in Frameworks */,
+				1A7057E7266167540070FD5D /* Feedbacks in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -297,6 +298,7 @@
 		7471829725AE7B0B0098E83E = {
 			isa = PBXGroup;
 			children = (
+				1A5E6478266166CA00F576A9 /* Feedbacks */,
 				747182A225AE7B0B0098E83E /* Examples */,
 				741C473E25EC5CDB00F1231B /* ExamplesTests */,
 				747182A125AE7B0B0098E83E /* Products */,
@@ -400,7 +402,7 @@
 			);
 			name = ExamplesTests;
 			packageProductDependencies = (
-				741C476525EC5E4C00F1231B /* FeedbacksTest */,
+				1A7057E8266167950070FD5D /* FeedbacksTest */,
 			);
 			productName = ExamplesTests;
 			productReference = 741C473D25EC5CDB00F1231B /* ExamplesTests.xctest */;
@@ -420,7 +422,7 @@
 			);
 			name = Examples;
 			packageProductDependencies = (
-				741C475B25EC5DE100F1231B /* Feedbacks */,
+				1A7057E6266167540070FD5D /* Feedbacks */,
 			);
 			productName = Examples;
 			productReference = 747182A025AE7B0B0098E83E /* Examples.app */;
@@ -454,7 +456,6 @@
 			);
 			mainGroup = 7471829725AE7B0B0098E83E;
 			packageReferences = (
-				741C475A25EC5DE100F1231B /* XCRemoteSwiftPackageReference "Feedbacks" */,
 			);
 			productRefGroup = 747182A125AE7B0B0098E83E /* Products */;
 			projectDirPath = "";
@@ -789,26 +790,13 @@
 		};
 /* End XCConfigurationList section */
 
-/* Begin XCRemoteSwiftPackageReference section */
-		741C475A25EC5DE100F1231B /* XCRemoteSwiftPackageReference "Feedbacks" */ = {
-			isa = XCRemoteSwiftPackageReference;
-			repositoryURL = "[email protected]:CombineCommunity/Feedbacks.git";
-			requirement = {
-				kind = exactVersion;
-				version = 0.3.0;
-			};
-		};
-/* End XCRemoteSwiftPackageReference section */
-
 /* Begin XCSwiftPackageProductDependency section */
-		741C475B25EC5DE100F1231B /* Feedbacks */ = {
+		1A7057E6266167540070FD5D /* Feedbacks */ = {
 			isa = XCSwiftPackageProductDependency;
-			package = 741C475A25EC5DE100F1231B /* XCRemoteSwiftPackageReference "Feedbacks" */;
 			productName = Feedbacks;
 		};
-		741C476525EC5E4C00F1231B /* FeedbacksTest */ = {
+		1A7057E8266167950070FD5D /* FeedbacksTest */ = {
 			isa = XCSwiftPackageProductDependency;
-			package = 741C475A25EC5DE100F1231B /* XCRemoteSwiftPackageReference "Feedbacks" */;
 			productName = FeedbacksTest;
 		};
 /* End XCSwiftPackageProductDependency section */

Examples/Examples.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -2,12 +2,21 @@
   "object": {
     "pins": [
       {
-        "package": "Feedbacks",
-        "repositoryURL": "git@github.com:CombineCommunity/Feedbacks.git",
+        "package": "combine-schedulers",
+        "repositoryURL": "https://github.com/pointfreeco/combine-schedulers.git",
         "state": {
           "branch": null,
-          "revision": "9d8ba9b4ada327b1f88401b822454770a6b65263",
-          "version": "0.3.0"
+          "revision": "ff42ec9061d864de7982162011321d3df5080c10",
+          "version": "0.1.2"
+        }
+      },
+      {
+        "package": "CombineExt",
+        "repositoryURL": "https://github.com/CombineCommunity/CombineExt.git",
+        "state": {
+          "branch": null,
+          "revision": "5b8a0c0f178527f9204200505c5fefa6847e528f",
+          "version": "1.3.0"
         }
       }
     ]

Examples/Examples/CounterApp/System/CounterApp+System.swift

@@ -5,6 +5,7 @@
 //  Created by Thibault Wittemberg on 2021-01-12.
 //
 
+import Dispatch
 import Feedbacks
 
 // define a namespace for this app's system
@@ -55,5 +56,5 @@ extension CounterApp.System {
                 On(CounterApp.Events.Decrease.self, transitionTo: CounterApp.States.Decreasing(counter: state.counter.decrease(), isPaused: false))
             }
         }
-    }
+    }.execute(on: DispatchQueue(label: "Counter Queue"))
 }

Examples/Examples/GiphyApp/Features/GifDetail/System/GifDetail+System.swift

@@ -32,10 +32,7 @@ extension GifDetail.System {
 
             Feedbacks {
                 Feedback(on: GifDetail.States.Loading.self, strategy: .cancelOnNewState, perform: loadSideEffect)
-                    .execute(on: DispatchQueue(label: "Load Gif Queue"))
-
                 Feedback(on: GifDetail.States.TogglingFavorite.self, strategy: .cancelOnNewState, perform: toggleFavoriteSideEffect)
-                    .execute(on: DispatchQueue(label: "Toggle Favorite Queue"))
             }
             .onStateReceived {
                 print("GifDetail: New state has been received: \($0)")
@@ -64,6 +61,6 @@ extension GifDetail.System {
                     On(GifDetail.Events.LoadingHasFailed.self, transitionTo: GifDetail.States.Failed())
                 }
             }
-        }
+        }.execute(on: DispatchQueue(label: "Load Gif Queue"))
     }
 }

Examples/Examples/GiphyApp/Features/GifList/System/GifList+System.swift

@@ -26,7 +26,6 @@ extension GifList.System {
 
             Feedbacks {
                 Feedback(on: GifList.States.Loading.self , strategy: .cancelOnNewState, perform: loadSideEffect)
-                    .execute(on: DispatchQueue(label: "Load Gifs Queue"))
             }
             .onStateReceived {
                 print("GifList: New state has been received: \($0)")
@@ -64,6 +63,6 @@ extension GifList.System {
                     On(GifList.Events.Refresh.self, transitionTo: GifList.States.Loading())
                 }
             }
-        }
+        }.execute(on: DispatchQueue(label: "Load Gifs Queue"))
     }
 }

Package.resolved

@@ -9,6 +9,15 @@
           "revision": "ff42ec9061d864de7982162011321d3df5080c10",
           "version": "0.1.2"
         }
+      },
+      {
+        "package": "CombineExt",
+        "repositoryURL": "https://github.com/CombineCommunity/CombineExt.git",
+        "state": {
+          "branch": null,
+          "revision": "5b8a0c0f178527f9204200505c5fefa6847e528f",
+          "version": "1.3.0"
+        }
       }
     ]
   },

Package.swift

@@ -23,13 +23,14 @@ let package = Package(
     dependencies: [
         // Dependencies declare other packages that this package depends on.
         .package(url: "https://github.com/pointfreeco/combine-schedulers.git", .exact(Version("0.1.2"))),
+        .package(url: "https://github.com/CombineCommunity/CombineExt.git", .exact(Version("1.3.0")))
     ],
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
         // Targets can depend on other targets in this package, and on products in packages this package depends on.
         .target(
             name: "Feedbacks",
-            dependencies: [],
+            dependencies: [.product(name: "CombineExt", package: "CombineExt")],
             path: "Sources/Feedbacks"),
         .testTarget(
             name: "FeedbacksTests",

README.md

@@ -96,9 +96,9 @@ In our example, one feedback takes care of increasing the volume and the other i
 
 ## Scheduling
 
-Threading is very important to make a nice responsive application. A Scheduler is the Combine way of handling threading by switching portions of reactive streams on dispatch queues, or operation queues or RunLoops.
+Threading is very important to make a nice responsive application. A Scheduler is the Combine way of handling threading by switching portions of reactive streams on dispatch queues, operation queues or RunLoops.
 
-The declarative syntax of Feedbacks allows to alter the behavior of side effects by simply applying modifiers (like you would do with SwiftUI to change the frame for instance). Modifying the scheduling of a side effect is as simple as calling the `.execute(on:)` modifier.
+The declarative syntax of Feedbacks allows to alter the behavior of a System by simply applying modifiers (like you would do with SwiftUI to change the frame for instance). Modifying the scheduling of a side effect is as simple as calling the `.execute(on:)` modifier.
 
 ```swift
 Feedbacks {
@@ -128,6 +128,52 @@ Feedbacks {
 
 Both side effects will be executed on the background queue.
 
+It is also applicable to the transitions:
+
+```swift
+Transitions {
+  From(VolumeState.self) { state in
+    On(IncreaseEvent.self, transitionTo: VolumeState(value: state.value + 1))
+    On(DecreaseEvent.self, transitionTo: VolumeState(value: state.value - 1))
+  }
+}.execute(on: DispatchQueue(label: "A background queue"))
+```
+
+ or to the whole system:
+
+ ```swift
+ System {
+  InitialState {
+    VolumeState(value: 10)
+  }
+
+  Feedbacks {
+    Feedback(on: VolumeState.self, strategy: .continueOnNewState) { state -> AnyPublisher<Event, Never> in
+      if state.value >= targetedVolume {
+        return Empty().eraseToAnyPublisher()
+      }
+
+      return Just(IncreaseEvent()).eraseToAnyPublisher()
+    }
+
+    Feedback(on: VolumeState.self, strategy: .continueOnNewState) { state -> AnyPublisher<Event, Never> in
+      if state.value <= targetedVolume {
+        return Empty().eraseToAnyPublisher()
+      }
+
+      return Just(DecreaseEvent()).eraseToAnyPublisher()
+    }
+  }
+
+  Transitions {
+    From(VolumeState.self) { state in
+      On(IncreaseEvent.self, transitionTo: VolumeState(value: state.value + 1))
+      On(DecreaseEvent.self, transitionTo: VolumeState(value: state.value - 1))
+    }
+  }
+}.execute(on: DispatchQueue(label: "A background queue"))
+ ```
+
 ## Lifecycle
 
 There are typical cases where a side effect consist of an asynchronous operation (like a network call). What happens if the very same side effect is called repeatedly, not waiting for the previous ones to end? Are the operations stacked? Are they cancelled when a new one is performed?
@@ -196,9 +242,9 @@ Here is a list of the supported modifiers:
 | Modifier | Action | Can be applied to |
 | -------------- | -------------- | -------------- |
 | `.disable(disabled:)`| The target won't be executed as long as the `disabled` condition is true | <ul align="left"><li>Transition</li><li>Transitions</li><li>Feedback</li></ul> |
-| `.execute(on:)`| The target will be executed on the scheduler | <ul align="left"><li>Feedbacks</li><li>Feedback</li></ul> |
-| `.onStateReceived(perform:)`| Execute the `perform` closure each time a new state is given as an input | <ul align="left"><li>Feedbacks</li><li>Feedback</li></ul> |
-| `.onEventEmitted(perform:)`| Execute the `perform` closure each time a new event is emitted | <ul align="left"><li>Feedbacks</li><li>Feedback</li></ul> |
+| `.execute(on:)`| The target will be executed on the scheduler | <ul align="left"><li>Transitions</li><li>Feedback</li><li>Feedbacks</li><li>System</li></ul> |
+| `.onStateReceived(perform:)`| Execute the `perform` closure each time a new state is given as an input | <ul align="left"><li>Feedback</li><li>Feedbacks</li></ul> |
+| `.onEventEmitted(perform:)`| Execute the `perform` closure each time a new event is emitted | <ul align="left"><li>Feedback</li><li>Feedbacks</li></ul> |
 | `.attach(to:)`| Refer to the "How to make systems communicate" section | <ul align="left"><li>System</li><li>UISystem</li></ul> |
 | `.uiSystem(viewStateFactory:)`| Refer to the "Using Feedbacks with SwiftUI and UIKit" section | <ul align="left"><li>System</li></ul> |
 

Sources/Feedbacks/System/System.swift

@@ -6,6 +6,7 @@
 //
 
 import Combine
+import CombineExt
 import Dispatch
 import Foundation
 
@@ -17,37 +18,26 @@ import Foundation
 public class System {
     let initialState: InitialState
     var feedbacks: Feedbacks
-    public let transitions: Transitions
-    var scheduledStream: (AnyPublisher<Event, Never>) -> AnyPublisher<Event, Never>
+    public private(set) var transitions: Transitions
 
     private var subscriptions = [AnyCancellable]()
 
-    static let defaultQueue = DispatchQueue(label: "Feedbacks.System.\(UUID().uuidString)")
-
     /// Builds a System based on its three components: an initial state, some feedbacks, a state machine
     /// By default, the System will be executed an a serial background queue. This can be altered thanks to the `.execute(on:)` modifier.
     /// - Parameter components: the three components of the System
     public convenience init(@SystemBuilder _ components: () -> (InitialState, Feedbacks, Transitions)) {
         let (initialState, feedbacks, transitions) = System.decode(builder: components)
         self.init(initialState: initialState,
                   feedbacks: feedbacks,
-                  transitions: transitions,
-                  scheduledStream: { (events: AnyPublisher<Event, Never>) in
-                    events
-                        .subscribe(on: System.defaultQueue)
-                        .receive(on: System.defaultQueue)
-                        .eraseToAnyPublisher()
-                  })
+                  transitions: transitions)
     }
 
     init(initialState: InitialState,
          feedbacks: Feedbacks,
-         transitions: Transitions,
-         scheduledStream: @escaping (AnyPublisher<Event, Never>) -> AnyPublisher<Event, Never>) {
+         transitions: Transitions) {
         self.initialState = initialState
         self.feedbacks = feedbacks
         self.transitions = transitions
-        self.scheduledStream = scheduledStream
     }
 
     static func decode(builder system: () -> (InitialState, Feedbacks, Transitions)) -> (InitialState, Feedbacks, Transitions) {
@@ -61,16 +51,15 @@ public extension System {
     /// Once this stream has been subscribed to, the initial state is given as an input to the feedbacks.
     /// Then the feedbacks can publish event that will trigger some transitions, generating a new state, and so on and so forth.
     var stream: AnyPublisher<State, Never> {
-        Deferred<AnyPublisher<State, Never>> { [initialState, feedbacks, transitions, scheduledStream] in
-            let currentState = CurrentValueSubject<State, Never>(initialState.value)
+        Deferred<AnyPublisher<State, Never>> { [initialState, feedbacks, transitions] in
+            let currentState = ReplaySubject<State, Never>(bufferSize: 1)
 
             // merging all the effects into one event stream
             let stateInputStream = currentState.eraseToAnyPublisher()
             let eventStream = feedbacks.eventStream(stateInputStream)
-            let scheduledEventStream = scheduledStream(eventStream)
 
-            return scheduledEventStream
-                .scan(initialState.value, transitions.reducer)
+            return transitions.scheduledReducer(initialState.value, eventStream)
+                .prepend(initialState.value)
                 .handleEvents(receiveOutput: currentState.send)
                 .eraseToAnyPublisher()
         }.eraseToAnyPublisher()
@@ -83,6 +72,14 @@ public extension System {
         self.stream.sink(receiveValue: { _ in }).store(in: &self.subscriptions)
         return self
     }
+
+    /// Subscribes to the state stream and store the cancellable in the System.
+    /// The subscription will be canceled once the System is deinit.
+    @discardableResult
+    func run<SchedulerType: Scheduler>(subscribeOn scheduler: SchedulerType) -> Self {
+        self.stream.subscribe(on: scheduler).sink(receiveValue: { _ in }).store(in: &self.subscriptions)
+        return self
+    }
 }
 
 // MARK: modifiers
@@ -93,13 +90,8 @@ public extension System {
     /// - Parameter scheduler: the scheduler on which to execute the System
     /// - Returns: The newly scheduled System
     func execute<SchedulerType: Scheduler>(on scheduler: SchedulerType) -> Self {
-        self.scheduledStream = { events in
-            events
-                .subscribe(on: scheduler)
-                .receive(on: scheduler)
-                .eraseToAnyPublisher()
-        }
-
+        self.feedbacks = self.feedbacks.execute(on: scheduler)
+        self.transitions = self.transitions.execute(on: scheduler)
         return self
     }