Conveniences for creating state machine as Property.

Example/PaginationViewController.swift

@@ -63,6 +63,7 @@ final class PaginationViewModel {
     private let nearBottomObserver: Signal<Void, NoError>.Observer
     private let retryObserver: Signal<Void, NoError>.Observer
 
+    private let stateProperty: Property<State>
     let movies: Property<[Movie]>
     let errors: Property<NSError?>
     let refreshing: Property<Bool>
@@ -88,24 +89,16 @@ final class PaginationViewModel {
             Feedbacks.retryFeedback(for: retrySignal),
             Feedbacks.retryPagingFeedback()
         ]
-        let initialState = State.initial
-        let stateProducer = SignalProducer.system(initial: initialState,
-                                                  reduce: State.reduce,
-                                                  feedbacks: feedbacks)
-            .observe(on: QueueScheduler.main)
 
-        let stateProperty = Property<State>(initial: initialState, then: stateProducer)
+        self.stateProperty = Property(initial: State.initial,
+                                      reduce: State.reduce,
+                                      feedbacks: feedbacks)
 
-        self.movies = Property<[Movie]>.init(initial: [], then: stateProperty.signal.filterMap {
-            $0.newMovies
-        })
+        self.movies = Property<[Movie]>(initial: [],
+                                        then: stateProperty.producer.filterMap { $0.newMovies })
 
-        self.errors = Property<NSError?>.init(initial: nil, then: stateProperty.producer.map {
-            $0.lastError
-        })
-        self.refreshing = stateProperty.map {
-            $0.isRefreshing
-        }
+        self.errors = stateProperty.map { $0.lastError }
+        self.refreshing = stateProperty.map { $0.isRefreshing }
         self.nearBottomObserver = nearBottomObserver
         self.retryObserver = retryObserver
     }

Example/ViewController.swift

@@ -42,6 +42,7 @@ class ViewController: UIViewController {
 }
 
 final class ViewModel {
+    private let state: Property<Int>
     let counter: Property<String>
 
     init(increment: Signal<Void, NoError>, decrement: Signal<Void, NoError>) {
@@ -56,12 +57,11 @@ final class ViewModel {
                 return decrement.map { _ in Event.decrement }
         }
 
-        let state = SignalProducer.system(initial: 0,
-                                          reduce: IncrementReducer.reduce,
-                                          feedbacks: incrementFeedback, decrementFeedback)
-            .map(String.init)
+        self.state = Property(initial: 0,
+                              reduce: IncrementReducer.reduce,
+                              feedbacks: incrementFeedback, decrementFeedback)
 
-        self.counter = Property(initial: "", then: state)
+        self.counter = state.map(String.init)
 
     }
 }

ReactiveFeedback.xcodeproj/project.pbxproj

@@ -16,6 +16,8 @@
 		5898B6D11F97ADDD005EEAEC /* SystemTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5898B6D01F97ADDD005EEAEC /* SystemTests.swift */; };
 		9A4CCB0B1F95D5CA00ACF758 /* Nimble.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 9A4CCB0C1F95D5CA00ACF758 /* Nimble.framework */; };
 		9A4CCB0D1F95D5D500ACF758 /* Nimble.framework in CopyFiles */ = {isa = PBXBuildFile; fileRef = 9A4CCB0C1F95D5CA00ACF758 /* Nimble.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
+		9AD5D42D1F97375E00E6AE5A /* Property+System.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9AD5D42C1F97375E00E6AE5A /* Property+System.swift */; };
+		9AE181B91F95A71B00A07551 /* ReactiveFeedbackTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9AE181B81F95A71B00A07551 /* ReactiveFeedbackTests.swift */; };
 		9AE181BB1F95A71B00A07551 /* ReactiveFeedback.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 25CC87AE1F92855300A6EBFC /* ReactiveFeedback.framework */; };
 		9AE181C21F95A77500A07551 /* ReactiveSwift.framework in CopyFiles */ = {isa = PBXBuildFile; fileRef = 9AFA212A1F95135B001DBF7C /* ReactiveSwift.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
 		9AE181C31F95A77500A07551 /* Result.framework in CopyFiles */ = {isa = PBXBuildFile; fileRef = 9AFA212B1F95135B001DBF7C /* Result.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
@@ -98,6 +100,7 @@
 		25E1D2371F56091A00D90192 /* PaginationViewController.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PaginationViewController.swift; sourceTree = "<group>"; };
 		5898B6D01F97ADDD005EEAEC /* SystemTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SystemTests.swift; sourceTree = "<group>"; };
 		9A4CCB0C1F95D5CA00ACF758 /* Nimble.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = Nimble.framework; sourceTree = BUILT_PRODUCTS_DIR; };
+		9AD5D42C1F97375E00E6AE5A /* Property+System.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Property+System.swift"; sourceTree = "<group>"; };
 		9AE181B61F95A71B00A07551 /* ReactiveFeedbackTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = ReactiveFeedbackTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		9AE181BA1F95A71B00A07551 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		9AFA21251F9511A5001DBF7C /* ReactiveFeedback.podspec */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = ReactiveFeedback.podspec; sourceTree = "<group>"; };
@@ -150,6 +153,7 @@
 			children = (
 				A95097E70D3CBFF05FA7B8CC /* Feedback.swift */,
 				A9509880213192F0D80EC2B3 /* SignalProducer+System.swift */,
+				9AD5D42C1F97375E00E6AE5A /* Property+System.swift */,
 				25CC87B11F92855300A6EBFC /* Info.plist */,
 			);
 			path = ReactiveFeedback;
@@ -359,6 +363,7 @@
 			files = (
 				A9509BE4551098F4A5503820 /* Feedback.swift in Sources */,
 				A950943401765BB90FA846B2 /* SignalProducer+System.swift in Sources */,
+				9AD5D42D1F97375E00E6AE5A /* Property+System.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

ReactiveFeedback/Property+System.swift

@@ -0,0 +1,28 @@
+import ReactiveSwift
+
+extension Property {
+    public convenience init<Event>(
+        initial: Value,
+        scheduler: Scheduler = QueueScheduler.main,
+        reduce: @escaping (Value, Event) -> Value,
+        feedbacks: [Feedback<Value, Event>]
+    ) {
+        let state = MutableProperty(initial)
+        state <~ SignalProducer.system(initial: initial,
+                                       scheduler: scheduler,
+                                       reduce: reduce,
+                                       feedbacks: feedbacks)
+            .skip(first: 1)
+
+        self.init(capturing: state)
+    }
+
+    public convenience init<Event>(
+        initial: Value,
+        scheduler: Scheduler = QueueScheduler.main,
+        reduce: @escaping (Value, Event) -> Value,
+        feedbacks: Feedback<Value, Event>...
+    ) {
+        self.init(initial: initial, scheduler: scheduler, reduce: reduce, feedbacks: feedbacks)
+    }
+}

ReactiveFeedback/SignalProducer+System.swift

@@ -10,7 +10,7 @@ extension SignalProducer where Error == NoError {
         feedbacks: [Feedback<Value, Event>]
     ) -> SignalProducer<Value, NoError> {
         return SignalProducer.deferred {
-            let (state, observer) = Signal<Value, NoError>.pipe()
+            let (state, stateObserver) = Signal<Value, NoError>.pipe()
 
             let events = feedbacks.map { feedback in
                 return feedback.events(scheduler, state)
@@ -19,7 +19,7 @@ extension SignalProducer where Error == NoError {
             return SignalProducer<Event, NoError>(Signal.merge(events))
                 .scan(initial, reduce)
                 .prefix(value: initial)
-                .on(value: observer.send(value:))
+                .on(value: stateObserver.send(value:))
         }
     }
 
@@ -30,11 +30,8 @@ extension SignalProducer where Error == NoError {
     ) -> SignalProducer<Value, Error> {
         return system(initial: initial, reduce: reduce, feedbacks: feedbacks)
     }
-}
 
-extension SignalProducerProtocol {
-    static func deferred(_ signalProducerFactory: @escaping () -> SignalProducer<Value, Error>) -> SignalProducer<Value, Error> {
-        return SignalProducer<Void, Error>(value: ())
-            .flatMap(.merge, signalProducerFactory)
+    private static func deferred(_ producer: @escaping () -> SignalProducer<Value, Error>) -> SignalProducer<Value, Error> {
+        return SignalProducer { $1 += producer().start($0) }
     }
 }