Implemented: TakeWhile

language-adaptors/rxjava-groovy/src/main/java/rx/lang/groovy/GroovyAdaptor.java

@@ -178,6 +178,22 @@ public void testTakeViaGroovy() {
             verify(assertion, times(0)).received(3);
         }
 
+        @Test
+        public void testTakeWhileViaGroovy() {
+            runGroovyScript("o.takeWhile(o.toObservable(1, 2, 3), { x -> x < 3}).subscribe({ result -> a.received(result)});");
+            verify(assertion, times(1)).received(1);
+            verify(assertion, times(1)).received(2);
+            verify(assertion, times(0)).received(3);
+        }
+
+        @Test
+        public void testTakeWhileWithIndexViaGroovy() {
+            runGroovyScript("o.takeWhileWithIndex(o.toObservable(1, 2, 3), { x, i -> i < 2}).subscribe({ result -> a.received(result)});");
+            verify(assertion, times(1)).received(1);
+            verify(assertion, times(1)).received(2);
+            verify(assertion, times(0)).received(3);
+        }
+
         @Test
         public void testToSortedList() {
             runGroovyScript("mockApiCall.getNumbers().toSortedList().subscribe({ result -> a.received(result)});");

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

@@ -1325,6 +1325,35 @@ public static <T> Observable<T> take(final Observable<T> items, final int num) {
         return create(OperationTake.take(items, num));
     }
 
+    public static <T> Observable<T> takeWhile(final Observable<T> items, Func1<T, Boolean> predicate) {
+        return create(OperationTake.takeWhile(items, predicate));
+    }
+
+    public static <T> Observable<T> takeWhile(final Observable<T> items, Object predicate) {
+        final FuncN _f = Functions.from(predicate);
+
+        return takeWhile(items, new Func1<T, Boolean>() {
+            @Override
+            public Boolean call(T t) {
+                return (Boolean) _f.call(t);
+            }
+        });
+    }
+    public static <T> Observable<T> takeWhileWithIndex(final Observable<T> items, Func2<T, Integer, Boolean> predicate) {
+        return create(OperationTake.takeWhileWithIndex(items, predicate));
+    }
+
+    public static <T> Observable<T> takeWhileWithIndex(final Observable<T> items, Object predicate) {
+        final FuncN _f = Functions.from(predicate);
+
+        return create(OperationTake.takeWhileWithIndex(items, new Func2<T, Integer, Boolean>() {
+            @Override
+            public Boolean call(T t, Integer integer) {
+                return (Boolean) _f.call(t, integer);
+            }
+        }));
+    }
+
     /**
      * Returns an Observable that emits a single item, a list composed of all the items emitted by
      * the source Observable.
@@ -2213,6 +2242,35 @@ public Observable<T> take(final int num) {
         return take(this, num);
     }
 
+
+    /**
+     * Returns an Observable that items emitted by the source Observable as long as a specified condition is true.
+     *
+     * @param predicate a function to test each source element for a condition
+     * @return
+     */
+    public Observable<T> takeWhile(final Func1<T, Boolean> predicate) {
+        return takeWhile(this, predicate);
+    }
+
+    public Observable<T> takeWhile(final Object predicate) {
+        return takeWhile(this, predicate);
+    }
+
+    /**
+     * Returns an Observable that items emitted by the source Observable as long as a specified condition is true.
+     *
+     * @param predicate true to the function to test each element for a condition; the second parameter of the function represents the index of the source element; otherwise, false.
+     * @return
+     */
+    public Observable<T> takeWhileWithIndex(final Func2<T, Integer, Boolean> predicate) {
+        return takeWhileWithIndex(this, predicate);
+    }
+
+    public Observable<T> takeWhileWithIndex(final Object predicate) {
+        return takeWhileWithIndex(this, predicate);
+    }
+
     /**
      * Returns an Observable that emits a single item, a list composed of all the items emitted by
      * the source Observable.

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

@@ -1,12 +1,12 @@
 /**
  * Copyright 2013 Netflix, Inc.
- * 
+ *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  * http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -28,33 +28,77 @@
 import rx.Subscription;
 import rx.util.AtomicObservableSubscription;
 import rx.util.functions.Func1;
+import rx.util.functions.Func2;
 
 /**
  * Returns a specified number of contiguous values from the start of an observable sequence.
- * 
+ *
  * @param <T>
  */
 public final class OperationTake {
 
     /**
      * Returns a specified number of contiguous values from the start of an observable sequence.
-     * 
+     *
      * @param items
      * @param num
      * @return
      */
     public static <T> Func1<Observer<T>, Subscription> take(final Observable<T> items, final int num) {
+        return takeWhileWithIndex(items, OperationTake.<T>numPredicate(num));
+    }
+
+    /**
+     * Returns a specified number of contiguous values from the start of an observable sequence.
+     *
+     * @param items
+     * @param predicate a function to test each source element for a condition
+     * @return
+     */
+    public static <T> Func1<Observer<T>, Subscription> takeWhile(final Observable<T> items, final Func1<T, Boolean> predicate) {
+        return takeWhileWithIndex(items, OperationTake.<T>skipIndex(predicate));
+    }
+
+    /**
+     * Returns values from an observable sequence as long as a specified condition is true, and then skips the remaining values.
+     *
+     * @param items
+     * @param predicate true to the function to test each element for a condition; the second parameter of the function represents the index of the source element; otherwise, false.
+     * @return
+     */
+    public static <T> Func1<Observer<T>, Subscription> takeWhileWithIndex(final Observable<T> items, final Func2<T, Integer, Boolean> predicate) {
         // wrap in a Watchbable so that if a chain is built up, then asynchronously subscribed to twice we will have 2 instances of Take<T> rather than 1 handing both, which is not thread-safe.
         return new Func1<Observer<T>, Subscription>() {
 
             @Override
             public Subscription call(Observer<T> observer) {
-                return new Take<T>(items, num).call(observer);
+                return new TakeWhile<T>(items, predicate).call(observer);
             }
 
         };
     }
 
+    private static <T> Func2<T, Integer, Boolean> numPredicate(final int num) {
+        return new Func2<T, Integer, Boolean>() {
+
+            @Override
+            public Boolean call(T input, Integer index) {
+                return index < num;
+            }
+
+        };
+    }
+
+    private static <T> Func2<T, Integer, Boolean> skipIndex(final Func1<T, Boolean> underlying) {
+        return new Func2<T, Integer, Boolean>() {
+            @Override
+            public Boolean call(T input, Integer index) {
+                return underlying.call(input);
+            }
+        };
+    }
+
+
     /**
      * This class is NOT thread-safe if invoked and referenced multiple times. In other words, don't subscribe to it multiple times from different threads.
      * <p>
@@ -63,29 +107,27 @@ public Subscription call(Observer<T> observer) {
      * This should all be fine as long as it's kept as a private class and a new instance created from static factory method above.
      * <p>
      * Note how the take() factory method above protects us from a single instance being exposed with the Observable wrapper handling the subscribe flow.
-     * 
+     *
      * @param <T>
      */
-    private static class Take<T> implements Func1<Observer<T>, Subscription> {
-        private final int num;
+    private static class TakeWhile<T> implements Func1<Observer<T>, Subscription> {
+        private final AtomicInteger counter = new AtomicInteger();
         private final Observable<T> items;
+        private final Func2<T, Integer, Boolean> predicate;
         private final AtomicObservableSubscription subscription = new AtomicObservableSubscription();
 
-        Take(final Observable<T> items, final int num) {
-            this.num = num;
+        private TakeWhile(Observable<T> items, Func2<T, Integer, Boolean> predicate) {
             this.items = items;
+            this.predicate = predicate;
         }
 
+
+        @Override
         public Subscription call(Observer<T> observer) {
             return subscription.wrap(items.subscribe(new ItemObserver(observer)));
         }
 
-        /**
-         * Used to subscribe to the 'items' Observable sequence and forward to the actualObserver up to 'num' count.
-         */
         private class ItemObserver implements Observer<T> {
-
-            private AtomicInteger counter = new AtomicInteger();
             private final Observer<T> observer;
 
             public ItemObserver(Observer<T> observer) {
@@ -104,7 +146,7 @@ public void onError(Exception e) {
 
             @Override
             public void onNext(T args) {
-                if (counter.getAndIncrement() < num) {
+                if (predicate.call(args, counter.getAndIncrement())) {
                     observer.onNext(args);
                 } else {
                     // this will work if the sequence is asynchronous, it will have no effect on a synchronous observable
@@ -118,6 +160,48 @@ public void onNext(T args) {
 
     public static class UnitTest {
 
+
+
+        @Test
+        public void testTakeWhile1() {
+            Observable<Integer> w = Observable.toObservable(1, 2, 3);
+            Observable<Integer> take = Observable.create(takeWhile(w, new Func1<Integer, Boolean>() {
+                @Override
+                public Boolean call(Integer input) {
+                    return input < 3;
+                }
+            }));
+
+            @SuppressWarnings("unchecked")
+            Observer<Integer> aObserver = mock(Observer.class);
+            take.subscribe(aObserver);
+            verify(aObserver, times(1)).onNext(1);
+            verify(aObserver, times(1)).onNext(2);
+            verify(aObserver, never()).onNext(3);
+            verify(aObserver, never()).onError(any(Exception.class));
+            verify(aObserver, times(1)).onCompleted();
+        }
+
+        @Test
+        public void testTakeWhile2() {
+            Observable<String> w = Observable.toObservable("one", "two", "three");
+            Observable<String> take = Observable.create(takeWhileWithIndex(w, new Func2<String, Integer, Boolean>() {
+                @Override
+                public Boolean call(String input, Integer index) {
+                    return index < 2;
+                }
+            }));
+
+            @SuppressWarnings("unchecked")
+            Observer<String> aObserver = mock(Observer.class);
+            take.subscribe(aObserver);
+            verify(aObserver, times(1)).onNext("one");
+            verify(aObserver, times(1)).onNext("two");
+            verify(aObserver, never()).onNext("three");
+            verify(aObserver, never()).onError(any(Exception.class));
+            verify(aObserver, times(1)).onCompleted();
+        }
+
         @Test
         public void testTake1() {
             Observable<String> w = Observable.toObservable("one", "two", "three");