Merge pull request ReactiveX#303 from benjchristensen/pull-267-combin…

…eLatest

Pull 267 - Merge combineLatest

rxjava-core/src/main/java/rx/Observable.java

@@ -43,6 +43,7 @@
 import rx.operators.AtomicObserver;
 import rx.operators.OperationAll;
 import rx.operators.OperationCache;
+import rx.operators.OperationCombineLatest;
 import rx.operators.OperationConcat;
 import rx.operators.OperationDefer;
 import rx.operators.OperationDematerialize;
@@ -2803,7 +2804,36 @@ public static <R> Observable<R> zip(Collection<Observable<?>> ws, final Object f
     }
 
     /**
-     * Filters an Observable by discarding any items it emits that do not meet some test.
+     * Combines the given observables, emitting an event containing an aggregation of the latest values of each of the source observables
+     * each time an event is received from one of the source observables, where the aggregation is defined by the given function.
+     * @param w0 
+     *          The first source observable.
+     * @param w1 
+     *          The second source observable.
+     * @param combineFunction 
+     *          The aggregation function used to combine the source observable values.
+     * @return A function from an observer to a subscription. This can be used to create an observable from.
+     */
+    public static <R, T0, T1> Observable<R> combineLatest(Observable<? super T0> w0, Observable<? super T1> w1, Func2<? super T0, ? super T1, ? extends R> combineFunction) {
+        return create(OperationCombineLatest.combineLatest(w0, w1, combineFunction));
+    }
+
+    /**
+     * @see #combineLatest(Observable, Observable, Func2)
+     */
+    public static <R, T0, T1, T2> Observable<R> combineLatest(Observable<? super T0> w0, Observable<? super T1> w1, Observable<? super T2> w2, Func3<? super T0, ? super T1, ? super T2, ? extends R> combineFunction) {
+        return create(OperationCombineLatest.combineLatest(w0, w1, w2, combineFunction));
+    }
+
+    /**
+     * @see #combineLatest(Observable, Observable, Func2)
+     */
+    public static <R, T0, T1, T2, T3> Observable<R> combineLatest(Observable<? super T0> w0, Observable<? super T1> w1, Observable<? super T2> w2, Observable<? super T3> w3, Func4<? super T0, ? super T1, ? super T2, ? super T3, ? extends R> combineFunction) {
+        return create(OperationCombineLatest.combineLatest(w0, w1, w2, w3, combineFunction));
+    }
+
+    /**
+     * Filters an Observable by discarding any of its emissions that do not meet some test.
      * <p>
      * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/filter.png">
      * 

rxjava-core/src/main/java/rx/operators/OperationCombineLatest.java

@@ -19,16 +19,16 @@
 import static org.mockito.Mockito.*;
 
 import java.util.Arrays;
-import java.util.HashMap;
-import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.junit.Test;
 import org.mockito.InOrder;
+import org.mockito.Matchers;
 
 import rx.Observable;
 import rx.Observer;
@@ -52,16 +52,17 @@
 public class OperationCombineLatest {
 
     /**
-     * Combines the two given Observables, emitting an item that aggregates the latest values of
-     * each of the source Observables each time an item is received from either of the source
-     * Observables, where the aggregation is defined by the given function.
-     * @param w0 the first source Observable.
-     * @param w1 the second source Observable.
-     * @param combineLatestFunction the aggregation function that combines the source Observable
-     *                              items.
-     * @return a function from an Observer to a Subscription. This can be used to create an Observable.
+     * Combines the two given observables, emitting an event containing an aggregation of the latest values of each of the source observables
+     * each time an event is received from one of the source observables, where the aggregation is defined by the given function.
+     * @param w0 
+     *          The first source observable.
+     * @param w1 
+     *          The second source observable.
+     * @param combineLatestFunction 
+     *          The aggregation function used to combine the source observable values.
+     * @return A function from an observer to a subscription. This can be used to create an observable from.
      */
-    public static <T0, T1, R> Func1<Observer<R>, Subscription> combineLatest(Observable<T0> w0, Observable<T1> w1, Func2<T0, T1, R> combineLatestFunction) {
+    public static <T0, T1, R> Func1<Observer<? super R>, Subscription> combineLatest(Observable<? super T0> w0, Observable<? super T1> w1, Func2<? super T0, ? super T1, ? extends R> combineLatestFunction) {
         Aggregator<R> a = new Aggregator<R>(Functions.fromFunc(combineLatestFunction));
         a.addObserver(new CombineObserver<R, T0>(a, w0));
         a.addObserver(new CombineObserver<R, T1>(a, w1));
@@ -71,7 +72,7 @@ public static <T0, T1, R> Func1<Observer<R>, Subscription> combineLatest(Observa
     /**
      * @see #combineLatest(Observable w0, Observable w1, Func2 combineLatestFunction)
      */
-    public static <T0, T1, T2, R> Func1<Observer<R>, Subscription> combineLatest(Observable<T0> w0, Observable<T1> w1, Observable<T2> w2, Func3<T0, T1, T2, R> combineLatestFunction) {
+    public static <T0, T1, T2, R> Func1<Observer<? super R>, Subscription> combineLatest(Observable<? super T0> w0, Observable<? super T1> w1, Observable<? super T2> w2, Func3<? super T0, ? super T1, ? super T2, ? extends R> combineLatestFunction) {
         Aggregator<R> a = new Aggregator<R>(Functions.fromFunc(combineLatestFunction));
         a.addObserver(new CombineObserver<R, T0>(a, w0));
         a.addObserver(new CombineObserver<R, T1>(a, w1));
@@ -82,7 +83,7 @@ public static <T0, T1, T2, R> Func1<Observer<R>, Subscription> combineLatest(Obs
     /**
      * @see #combineLatest(Observable w0, Observable w1, Func2 combineLatestFunction)
      */
-    public static <T0, T1, T2, T3, R> Func1<Observer<R>, Subscription> combineLatest(Observable<T0> w0, Observable<T1> w1, Observable<T2> w2, Observable<T3> w3, Func4<T0, T1, T2, T3, R> combineLatestFunction) {
+    public static <T0, T1, T2, T3, R> Func1<Observer<? super R>, Subscription> combineLatest(Observable<? super T0> w0, Observable<? super T1> w1, Observable<? super T2> w2, Observable<? super T3> w3, Func4<? super T0, ? super T1, ? super T2, ? super T3, ? extends R> combineLatestFunction) {
         Aggregator<R> a = new Aggregator<R>(Functions.fromFunc(combineLatestFunction));
         a.addObserver(new CombineObserver<R, T0>(a, w0));
         a.addObserver(new CombineObserver<R, T1>(a, w1));
@@ -92,16 +93,16 @@ public static <T0, T1, T2, T3, R> Func1<Observer<R>, Subscription> combineLatest
     }
 
     private static class CombineObserver<R, T> implements Observer<T> {
-        final Observable<T> w;
-        final Aggregator<R> a;
+        final Observable<? super T> w;
+        final Aggregator<? super R> a;
         private Subscription subscription;
 
-        public CombineObserver(Aggregator<R> a, Observable<T> w) {
+        public CombineObserver(Aggregator<? super R> a, Observable<? super T> w) {
             this.a = a;
             this.w = w;
         }
 
-        public synchronized void startWatching() {
+        private void startWatching() {
             if (subscription != null) {
                 throw new RuntimeException("This should only be called once.");
             }
@@ -129,44 +130,28 @@ public void onNext(T args) {
      * whenever we have received an event from one of the observables, as soon as each Observable has received 
      * at least one event.
      */
-    private static class Aggregator<R> implements Func1<Observer<R>, Subscription> {
+    private static class Aggregator<R> implements Func1<Observer<? super R>, Subscription> {
 
-        private Observer<R> observer;
+        private volatile Observer<? super R> observer;
 
-        private final FuncN<R> combineLatestFunction;
+        private final FuncN<? extends R> combineLatestFunction;
         private final AtomicBoolean running = new AtomicBoolean(true);
-
-        // used as an internal lock for handling the latest values and the completed state of each observer
-        private final Object lockObject = new Object();
 
-        /**
-         * Store when an observer completes.
-         * <p>
-         * Note that access to this set MUST BE SYNCHRONIZED via 'lockObject' above.
-         * */
-        private final Set<CombineObserver<R, ?>> completed = new HashSet<CombineObserver<R, ?>>();
-
-        /**
-         * The latest value from each observer
-         * <p>
-         * Note that access to this set MUST BE SYNCHRONIZED via 'lockObject' above.
-         * */
-        private final Map<CombineObserver<R, ?>, Object> latestValue = new HashMap<CombineObserver<R, ?>, Object>();
+        // Stores how many observers have already completed
+        private final AtomicInteger numCompleted = new AtomicInteger(0);
 
         /**
-         * Whether each observer has a latest value at all.
-         * <p>
-         * Note that access to this set MUST BE SYNCHRONIZED via 'lockObject' above.
-         * */
-        private final Set<CombineObserver<R, ?>> hasLatestValue = new HashSet<CombineObserver<R, ?>>();
-
+         * The latest value from each observer.
+         */
+        private final Map<CombineObserver<? extends R, ?>, Object> latestValue = new ConcurrentHashMap<CombineObserver<? extends R, ?>, Object>();
+
         /**
          * Ordered list of observers to combine.
          * No synchronization is necessary as these can not be added or changed asynchronously.
          */
         private final List<CombineObserver<R, ?>> observers = new LinkedList<CombineObserver<R, ?>>();
 
-        public Aggregator(FuncN<R> combineLatestFunction) {
+        public Aggregator(FuncN<? extends R> combineLatestFunction) {
             this.combineLatestFunction = combineLatestFunction;
         }
 
@@ -184,18 +169,15 @@ <T> void addObserver(CombineObserver<R, T> w) {
          * 
          * @param w The observer that has completed.
          */
-        <T> void complete(CombineObserver<R, T> w) {
-            synchronized(lockObject) {
-                // store that this CombineLatestObserver is completed
-                completed.add(w);
-                // if all CombineObservers are completed, we mark the whole thing as completed
-                if (completed.size() == observers.size()) {
-                    if (running.get()) {
-                        // mark ourselves as done
-                        observer.onCompleted();
-                        // just to ensure we stop processing in case we receive more onNext/complete/error calls after this
-                        running.set(false);
-                    }
+        <T> void complete(CombineObserver<? extends R, ? super T> w) {
+            int completed = numCompleted.incrementAndGet();
+            // if all CombineObservers are completed, we mark the whole thing as completed
+            if (completed == observers.size()) {
+                if (running.get()) {
+                    // mark ourselves as done
+                    observer.onCompleted();
+                    // just to ensure we stop processing in case we receive more onNext/complete/error calls after this
+                    running.set(false);
                 }
             }
         }
@@ -217,7 +199,7 @@ void error(Exception e) {
          * @param w
          * @param arg
          */
-        <T> void next(CombineObserver<R, T> w, T arg) {
+        <T> void next(CombineObserver<? extends R, ? super T> w, T arg) {
             if (observer == null) {
                 throw new RuntimeException("This shouldn't be running if an Observer isn't registered");
             }
@@ -227,54 +209,48 @@ <T> void next(CombineObserver<R, T> w, T arg) {
                 return;
             }
 
-            // define here so the variable is out of the synchronized scope
+            // remember this as the latest value for this observer
+            latestValue.put(w, arg);
+
+            if (latestValue.size() < observers.size()) {
+              // we don't have a value yet for each observer to combine, so we don't have a combined value yet either
+              return;
+            }
+
             Object[] argsToCombineLatest = new Object[observers.size()];
-
-            // we synchronize everything that touches latest values
-            synchronized (lockObject) {
-                // remember this as the latest value for this observer
-                latestValue.put(w, arg);
-
-                // remember that this observer now has a latest value set
-                hasLatestValue.add(w);
-
-                // if all observers in the 'observers' list have a value, invoke the combineLatestFunction
-                for (CombineObserver<R, ?> rw : observers) {
-                    if (!hasLatestValue.contains(rw)) {
-                        // we don't have a value yet for each observer to combine, so we don't have a combined value yet either
-                        return;
-                    }
-                }
-                // if we get to here this means all the queues have data
-                int i = 0;
-                for (CombineObserver<R, ?> _w : observers) {
-                    argsToCombineLatest[i++] = latestValue.get(_w);
-                }
+            int i = 0;
+            for (CombineObserver<R, ?> _w : observers) {
+                argsToCombineLatest[i++] = latestValue.get(_w);
+            }
+
+            try {
+                R combinedValue = combineLatestFunction.call(argsToCombineLatest);
+                observer.onNext(combinedValue);
+            } catch(Exception ex) {
+                observer.onError(ex);
             }
-            // if we did not return above from the synchronized block we can now invoke the combineLatestFunction with all of the args
-            // we do this outside the synchronized block as it is now safe to call this concurrently and don't need to block other threads from calling
-            // this 'next' method while another thread finishes calling this combineLatestFunction
-            observer.onNext(combineLatestFunction.call(argsToCombineLatest));
         }
 
         @Override
-        public Subscription call(Observer<R> observer) {
+        public Subscription call(Observer<? super R> observer) {
             if (this.observer != null) {
                 throw new IllegalStateException("Only one Observer can subscribe to this Observable.");
             }
-            this.observer = observer;
+
+            AtomicObservableSubscription subscription = new AtomicObservableSubscription(new Subscription() {
+                @Override
+                public void unsubscribe() {
+                    stop();
+                }
+            });
+            this.observer = new SynchronizedObserver<R>(observer, subscription);
 
             /* start the observers */
             for (CombineObserver<R, ?> rw : observers) {
                 rw.startWatching();
             }
 
-            return new Subscription() {
-                @Override
-                public void unsubscribe() {
-                    stop();
-                }
-            };
+            return subscription;
         }
 
         private void stop() {
@@ -291,10 +267,33 @@ private void stop() {
 
     public static class UnitTest {
 
-        @SuppressWarnings("unchecked")
-        /* mock calls don't do generics */
+        @Test
+        public void testCombineLatestWithFunctionThatThrowsAnException() {
+            @SuppressWarnings("unchecked") // mock calls don't do generics
+            Observer<String> w = mock(Observer.class);
+
+            TestObservable w1 = new TestObservable();
+            TestObservable w2 = new TestObservable();
+
+            Observable<String> combined = Observable.create(combineLatest(w1, w2, new Func2<String, String, String>() {
+                @Override
+                public String call(String v1, String v2) {
+                    throw new RuntimeException("I don't work.");
+                }
+            }));
+            combined.subscribe(w);
+
+            w1.Observer.onNext("first value of w1");
+            w2.Observer.onNext("first value of w2");
+
+            verify(w, never()).onNext(anyString());
+            verify(w, never()).onCompleted();
+            verify(w, times(1)).onError(Matchers.<RuntimeException>any());
+        }
+
         @Test
         public void testCombineLatestDifferentLengthObservableSequences1() {
+            @SuppressWarnings("unchecked") // mock calls don't do generics
             Observer<String> w = mock(Observer.class);
 
             TestObservable w1 = new TestObservable();

rxjava-core/src/main/java/rx/operators/SynchronizedObserver.java

@@ -64,12 +64,12 @@ public final class SynchronizedObserver<T> implements Observer<T> {
      * // TODO composing of this class should rarely happen now with updated design so this decision should be revisited
      */
 
-    private final Observer<T> observer;
+    private final Observer<? super T> observer;
     private final AtomicObservableSubscription subscription;
     private volatile boolean finishRequested = false;
     private volatile boolean finished = false;
 
-    public SynchronizedObserver(Observer<T> Observer, AtomicObservableSubscription subscription) {
+    public SynchronizedObserver(Observer<? super T> Observer, AtomicObservableSubscription subscription) {
         this.observer = Observer;
         this.subscription = subscription;
     }