Merge pull request ReactiveX#259 from michaeldejong/operation-switch

Added the switch operator to Observable

Author: benjchristensen

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

@@ -61,6 +61,7 @@
 import rx.operators.OperationScan;
 import rx.operators.OperationSkip;
 import rx.operators.OperationSubscribeOn;
+import rx.operators.OperationSwitch;
 import rx.operators.OperationSynchronize;
 import rx.operators.OperationTake;
 import rx.operators.OperationTakeLast;
@@ -1800,6 +1801,19 @@ public static <T> Observable<T> skip(final Observable<T> items, int num) {
         return create(OperationSkip.skip(items, num));
     }
 
+    /**
+     * Accepts an {@link Observable} sequence of {@link Observable} sequences, and transforms it into a single
+     * {@link Observable} sequence, which publishes the values of the most recently published {@link Observable} sequence.
+     *  
+     * @param sequenceOfSequences
+     *            the {@link Observable} sequence of {@link Observable} sequences.
+     * @return an {@link Observable} which publishes only the values of the most recently published 
+     *         {@link Observable} sequence.
+     */
+    public static <T> Observable<T> switchDo(Observable<Observable<T>> sequenceOfSequences) {
+        return create(OperationSwitch.switchDo(sequenceOfSequences));
+    }
+
     /**
      * Accepts an Observable and wraps it in another Observable that ensures that the resulting
      * Observable is chronologically well-behaved.