DoOn Tweaks

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

@@ -5023,33 +5023,58 @@ public void onNext(T args) {
 
         return create(OperationDoOnEach.doOnEach(this, observer));
     }
+
+    /**
+     * Invokes an action if onError is emitted from the observable sequence.
+     *
+     * @param onError
+     *            The action to invoke if onError is invoked.
+     *
+     * @return
+     *            The source sequence with the side-effecting behavior applied.
+     * @see <a href="http://msdn.microsoft.com/en-us/library/hh229804(v=vs.103).aspx">MSDN: Observable.Do</a>
+     */
+    public Observable<T> doOnError(final Action1<Throwable> onError) {
+        Observer<T> observer = new Observer<T>() {
+            @Override
+            public void onCompleted() {}
+
+            @Override
+            public void onError(Throwable e) {
+                onError.call(e);
+            }
 
+            @Override
+            public void onNext(T args) { }
+
+        };
+
+
+        return create(OperationDoOnEach.doOnEach(this, observer));
+    }
+
     /**
-     * Invokes an action for each element in the observable sequence.
+     * Invokes an action when onCompleted is emitted from the observable sequence.
      *
-     * @param onNext
-     *            The action to invoke for each element in the source sequence.
      * @param onCompleted
-     *            The action to invoke when the source sequence is completed.
+     *            The action to invoke when onCompleted is emitted.
      *
      * @return
      *            The source sequence with the side-effecting behavior applied.
-     * @see <a href="http://msdn.microsoft.com/en-us/library/hh229659(v=vs.103).aspx">MSDN: Observable.Do</a>
+     * @see <a href="http://msdn.microsoft.com/en-us/library/hh229804(v=vs.103).aspx">MSDN: Observable.Do</a>
      */
-    public Observable<T> doOnEach(final Action1<T> onNext, final Action0 onCompleted) {
+    public Observable<T> doOnCompleted(final Action0 onCompleted) {
         Observer<T> observer = new Observer<T>() {
             @Override
             public void onCompleted() {
                 onCompleted.call();
             }
 
             @Override
-            public void onError(Throwable e) {}
+            public void onError(Throwable e) { }
 
             @Override
-            public void onNext(T args) {
-                onNext.call(args);
-            }
+            public void onNext(T args) { }
 
         };
 

rxjava-core/src/test/java/rx/ObservableDoOnTest.java

@@ -0,0 +1,80 @@
+/**
+ * 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.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package rx;
+
+import static org.junit.Assert.*;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.junit.Test;
+
+import rx.util.functions.Action0;
+import rx.util.functions.Action1;
+
+public class ObservableDoOnTest {
+
+    @Test
+    public void testDoOnEach() {
+        final AtomicReference<String> r = new AtomicReference<String>();
+        String output = Observable.from("one").doOnEach(new Action1<String>() {
+
+            @Override
+            public void call(String v) {
+                r.set(v);
+            }
+        }).toBlockingObservable().single();
+
+        assertEquals("one", output);
+        assertEquals("one", r.get());
+    }
+
+    @Test
+    public void testDoOnError() {
+        final AtomicReference<Throwable> r = new AtomicReference<Throwable>();
+        Throwable t = null;
+        try {
+            Observable.<String> error(new RuntimeException("an error")).doOnError(new Action1<Throwable>() {
+
+                @Override
+                public void call(Throwable v) {
+                    r.set(v);
+                }
+            }).toBlockingObservable().single();
+            fail("expected exception, not a return value");
+        } catch (Throwable e) {
+            t = e;
+        }
+
+        assertNotNull(t);
+        assertEquals(t, r.get());
+    }
+
+    @Test
+    public void testDoOnCompleted() {
+        final AtomicBoolean r = new AtomicBoolean();
+        String output = Observable.from("one").doOnCompleted(new Action0() {
+
+            @Override
+            public void call() {
+                r.set(true);
+            }
+        }).toBlockingObservable().single();
+
+        assertEquals("one", output);
+        assertTrue(r.get());
+    }
+}