Merge pull request #275 from leontedev/master

Adds latest parameter for throttle

Author: srdanrasic

Sources/SignalProtocol+Filtering.swift

@@ -374,44 +374,71 @@ extension SignalProtocol {
         }
     }
 
-    /// Throttle the signal to emit at most one element per given `seconds` interval. Signal will emit latest element from each interval.
+    /// Throttle the signal to emit at most one element per given `seconds` interval. Emits either the most-recent or first element in the specified time interval.
+    ///
+    /// - parameter seconds:  The interval at which to find and emit either the most recent or the first element.
+    /// - parameter latest:  Defaults to `true`. A Bool value that indicates whether to publish the most recent element. If `false`, it emits the first element received during the interval. If `true` Signal will emit latest element from each interval.
     ///
     /// Check out interactive example at [https://rxmarbles.com/#throttle](https://rxmarbles.com/#throttle)
-    public func throttle(for seconds: Double, queue: DispatchQueue = DispatchQueue(label: "com.reactive_kit.signal.throttle")) -> Signal<Element, Error> {
-        return Signal { observer in
-            var isInitialElement = true
-            var throttledDisposable: Disposable? = nil
-            var lastElement: Element? = nil
-            var isFinished: Bool = false
-            return self.observe { event in
-                queue.async {
-                    switch event {
-                    case .next(let element):
-                        if isInitialElement {
-                            isInitialElement = false
-                            observer.receive(element)
-                        } else {
-                            lastElement = element
-                        }
-                        guard throttledDisposable == nil else { return }
-                        throttledDisposable = queue.disposableAfter(when: seconds) {
-                            if let element = lastElement {
+    public func throttle(
+        for seconds: Double,
+        queue: DispatchQueue = DispatchQueue(label: "com.reactive_kit.signal.throttle"),
+        latest: Bool = true
+    ) -> Signal<Element, Error> {
+        if latest {
+            return Signal { observer in
+                var isInitialElement = true
+                var throttledDisposable: Disposable? = nil
+                var lastElement: Element? = nil
+                var isFinished: Bool = false
+                return self.observe { event in
+                    queue.async {
+                        switch event {
+                        case .next(let element):
+                            if isInitialElement {
+                                isInitialElement = false
                                 observer.receive(element)
-                                lastElement = nil
+                            } else {
+                                lastElement = element
                             }
-                            if isFinished {
-                                observer.receive(completion: .finished)
+                            guard throttledDisposable == nil else { return }
+                            throttledDisposable = queue.disposableAfter(when: seconds) {
+                                if let element = lastElement {
+                                    observer.receive(element)
+                                    lastElement = nil
+                                }
+                                if isFinished {
+                                    observer.receive(completion: .finished)
+                                }
+                                throttledDisposable = nil
                             }
-                            throttledDisposable = nil
+                        case .failed(let error):
+                            observer.receive(completion: .failure(error))
+                        case .completed:
+                            guard throttledDisposable == nil else {
+                                isFinished = true
+                                return
+                            }
+                            observer.receive(completion: .finished)
                         }
-                    case .failed(let error):
-                        observer.receive(completion: .failure(error))
-                    case .completed:
-                        guard throttledDisposable == nil else {
-                            isFinished = true
-                            return
+                    }
+                }
+            }
+        } else {
+            return Signal { observer in
+                let lock = NSRecursiveLock(name: "com.reactive_kit.signal.throttle")
+                var _lastEventTime: DispatchTime?
+                return self.observe { event in
+                    switch event {
+                    case .next(let element):
+                        lock.lock(); defer { lock.unlock() }
+                        let now = DispatchTime.now()
+                        if _lastEventTime == nil || now.rawValue > (_lastEventTime! + seconds).rawValue {
+                            _lastEventTime = now
+                            observer.receive(element)
                         }
-                        observer.receive(completion: .finished)
+                    default:
+                        observer.on(event)
                     }
                 }
             }