Merge pull request #403 from zsxwing/cast

Implemented the 'cast' and 'ofType' operators

Author: benjchristensen

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

@@ -33,6 +33,7 @@
 import rx.operators.OperationAverage;
 import rx.operators.OperationBuffer;
 import rx.operators.OperationCache;
+import rx.operators.OperationCast;
 import rx.operators.OperationCombineLatest;
 import rx.operators.OperationConcat;
 import rx.operators.OperationDebounce;
@@ -4369,6 +4370,44 @@ public BlockingObservable<T> toBlockingObservable() {
         return BlockingObservable.from(this);
     }
 
+    /**
+     * Converts the elements of an observable sequence to the specified type.
+     *
+     * @param klass
+     *            The target class type which the elements will be converted to.
+     *
+     * @return An observable sequence that contains each element of the source
+     *         sequence converted to the specified type.
+     *
+     * @see <a
+     *      href="http://msdn.microsoft.com/en-us/library/hh211842(v=vs.103).aspx">MSDN:
+     *      Observable.Cast</a>
+     */
+    public <R> Observable<R> cast(final Class<R> klass) {
+        return create(OperationCast.cast(this, klass));
+    }
+
+    /**
+     * Filters the elements of an observable sequence based on the specified
+     * type.
+     *
+     * @param klass
+     *            The class type to filter the elements in the source sequence
+     *            on.
+     *
+     * @return An observable sequence that contains elements from the input
+     *         sequence of type klass.
+     *
+     * @see <a href="http://msdn.microsoft.com/en-us/library/hh229380(v=vs.103).aspx">MSDN: Observable.OfType</a>
+     */
+    public <R> Observable<R> ofType(final Class<R> klass) {
+        return filter(new Func1<T, Boolean>() {
+            public Boolean call(T t) {
+                return klass.isInstance(t);
+            }
+        }).cast(klass);
+    }
+
     /**
      * Whether a given {@link Function} is an internal implementation inside rx.* packages or not.
      * <p>

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

@@ -0,0 +1,61 @@
+package rx.operators;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import org.junit.Test;
+
+import rx.Observable;
+import rx.Observable.OnSubscribeFunc;
+import rx.Observer;
+import rx.util.functions.Func1;
+
+/**
+ * Converts the elements of an observable sequence to the specified type.
+ */
+public class OperationCast {
+
+    public static <T, R> OnSubscribeFunc<R> cast(
+            Observable<? extends T> source, final Class<R> klass) {
+        return OperationMap.map(source, new Func1<T, R>() {
+            public R call(T t) {
+                return klass.cast(t);
+            }
+        });
+    }
+
+    public static class UnitTest {
+
+        @Test
+        public void testCast() {
+            Observable<?> source = Observable.from(1, 2);
+            Observable<Integer> observable = Observable.create(cast(source,
+                    Integer.class));
+
+            @SuppressWarnings("unchecked")
+            Observer<Integer> aObserver = mock(Observer.class);
+            observable.subscribe(aObserver);
+            verify(aObserver, times(1)).onNext(1);
+            verify(aObserver, times(1)).onNext(1);
+            verify(aObserver, never()).onError(
+                    org.mockito.Matchers.any(Throwable.class));
+            verify(aObserver, times(1)).onCompleted();
+        }
+
+        @Test
+        public void testCastWithWrongType() {
+            Observable<?> source = Observable.from(1, 2);
+            Observable<Boolean> observable = Observable.create(cast(source,
+                    Boolean.class));
+
+            @SuppressWarnings("unchecked")
+            Observer<Boolean> aObserver = mock(Observer.class);
+            observable.subscribe(aObserver);
+            verify(aObserver, times(1)).onError(
+                    org.mockito.Matchers.any(ClassCastException.class));
+        }
+    }
+
+}

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

@@ -20,6 +20,8 @@
 import static org.mockito.Mockito.*;
 
 import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -701,4 +703,42 @@ public void onNext(String v) {
             fail("It should be a NumberFormatException");
         }
     }
+    
+    @Test
+    public void testOfType() {
+        Observable<String> observable = Observable.from(1, "abc", false, 2L).ofType(String.class);
+
+        @SuppressWarnings("unchecked")
+        Observer<Object> aObserver = mock(Observer.class);
+        observable.subscribe(aObserver);
+        verify(aObserver, never()).onNext(1);
+        verify(aObserver, times(1)).onNext("abc");
+        verify(aObserver, never()).onNext(false);
+        verify(aObserver, never()).onNext(2L);
+        verify(aObserver, never()).onError(
+                org.mockito.Matchers.any(Throwable.class));
+        verify(aObserver, times(1)).onCompleted();
+    }
+
+    @Test
+    public void testOfTypeWithPolymorphism() {
+        ArrayList<Integer> l1 = new ArrayList<Integer>();
+        l1.add(1);
+        LinkedList<Integer> l2 = new LinkedList<Integer>();
+        l2.add(2);
+
+        @SuppressWarnings("rawtypes")
+        Observable<List> observable = Observable.<Object>from(l1, l2, "123").ofType(List.class);
+
+        @SuppressWarnings("unchecked")
+        Observer<Object> aObserver = mock(Observer.class);
+        observable.subscribe(aObserver);
+        verify(aObserver, times(1)).onNext(l1);
+        verify(aObserver, times(1)).onNext(l2);
+        verify(aObserver, never()).onNext("123");
+        verify(aObserver, never()).onError(
+                org.mockito.Matchers.any(Throwable.class));
+        verify(aObserver, times(1)).onCompleted();
+    }
+
 }