Add maxConcurrent overload to flatMapIterable

Author: lukaciko

src/main/java/rx/Observable.java

@@ -5558,6 +5558,36 @@ public final <R> Observable<R> flatMapIterable(Func1<? super T, ? extends Iterab
         return merge(map(OperatorMapPair.convertSelector(collectionSelector)));
     }
 
+    /**
+     * Returns an Observable that merges each item emitted by the source Observable with the values in an
+     * Iterable corresponding to that item that is generated by a selector, while limiting the number of concurrent
+     * subscriptions to these Observables.
+     * <p>
+     * <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/mergeMapIterable.png" alt="">
+     * <dl>
+     *  <dt><b>Scheduler:</b></dt>
+     *  <dd>{@code flatMapIterable} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     *
+     * @param <R>
+     *            the type of item emitted by the resulting Observable
+     * @param collectionSelector
+     *            a function that returns an Iterable sequence of values for when given an item emitted by the
+     *            source Observable
+     * @param maxConcurrent
+     *            the maximum number of Observables that may be subscribed to concurrently
+     * @return an Observable that emits the results of merging the items emitted by the source Observable with
+     *         the values in the Iterables corresponding to those items, as generated by {@code collectionSelector}
+     * @throws IllegalArgumentException
+     *             if {@code maxConcurrent} is less than or equal to 0
+     * @see <a href="http://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>
+     * @since (if this graduates from Experimental/Beta to supported, replace this parenthetical with the release number)
+     */
+    @Beta
+    public final <R> Observable<R> flatMapIterable(Func1<? super T, ? extends Iterable<? extends R>> collectionSelector, int maxConcurrent) {
+        return merge(map(OperatorMapPair.convertSelector(collectionSelector)), maxConcurrent);
+    }
+    
     /**
      * Returns an Observable that emits the results of applying a function to the pair of values from the source
      * Observable and an Iterable corresponding to that item that is generated by a selector.
@@ -5587,6 +5617,42 @@ public final <U, R> Observable<R> flatMapIterable(Func1<? super T, ? extends Ite
         return flatMap(OperatorMapPair.convertSelector(collectionSelector), resultSelector);
     }
 
+    /**
+     * Returns an Observable that emits the results of applying a function to the pair of values from the source
+     * Observable and an Iterable corresponding to that item that is generated by a selector, while limiting the
+     * number of concurrent subscriptions to these Observables.
+     * <p>
+     * <img width="640" height="390" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/mergeMapIterable.r.png" alt="">
+     * <dl>
+     *  <dt><b>Scheduler:</b></dt>
+     *  <dd>{@code flatMapIterable} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     *
+     * @param <U>
+     *            the collection element type
+     * @param <R>
+     *            the type of item emited by the resulting Observable
+     * @param collectionSelector
+     *            a function that returns an Iterable sequence of values for each item emitted by the source
+     *            Observable
+     * @param resultSelector
+     *            a function that returns an item based on the item emitted by the source Observable and the
+     *            Iterable returned for that item by the {@code collectionSelector}
+     * @param maxConcurrent
+     *            the maximum number of Observables that may be subscribed to concurrently
+     * @return an Observable that emits the items returned by {@code resultSelector} for each item in the source
+     *         Observable
+     * @throws IllegalArgumentException
+     *             if {@code maxConcurrent} is less than or equal to 0
+     * @see <a href="http://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>
+     * @since (if this graduates from Experimental/Beta to supported, replace this parenthetical with the release number)
+     */
+    @Beta
+    public final <U, R> Observable<R> flatMapIterable(Func1<? super T, ? extends Iterable<? extends U>> collectionSelector,
+            Func2<? super T, ? super U, ? extends R> resultSelector, int maxConcurrent) {
+        return flatMap(OperatorMapPair.convertSelector(collectionSelector), resultSelector, maxConcurrent);
+    }
+
     /**
      * Subscribes to the {@link Observable} and receives notifications for each element.
      * <p>