Add unit test for MvpNullObjectBasePresenter

mvp-common/src/main/java/com/hannesdorfmann/mosby/mvp/Defaults.java

@@ -1,10 +1,32 @@
+/*
+ *  Copyright 2015. Hannes Dorfmann.
+ *
+ * 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 com.hannesdorfmann.mosby.mvp;
 
 import java.util.HashMap;
 import java.util.Map;
 
 import static java.util.Collections.unmodifiableMap;
 
+/**
+ * Helper class for default type values used by {@link NoOp}
+ * @author Jens Dirller
+ * @since 1.2.0
+ */
 final class Defaults {
 
   private static final Map<Class<?>, Object> DEFAULTS =

mvp/src/main/java/com/hannesdorfmann/mosby/mvp/MvpBasePresenter.java → mvp-common/src/main/java/com/hannesdorfmann/mosby/mvp/MvpBasePresenter.java

@@ -26,7 +26,9 @@
  * presenter before calling {@link #getView()} to access the view.
  * </p>
  *
+ * @param <V> type of the {@link MvpView}
  * @author Hannes Dorfmann
+ * @see MvpNullObjectBasePresenter
  * @since 1.0.0
  */
 public class MvpBasePresenter<V extends MvpView> implements MvpPresenter<V> {

mvp-common/src/main/java/com/hannesdorfmann/mosby/mvp/MvpNullObjectBasePresenter.java

@@ -1,11 +1,23 @@
 package com.hannesdorfmann.mosby.mvp;
 
+/**
+ * A {@link MvpPresenter} implmenetation that implements the <a href="https://en.wikipedia.org/wiki/Null_Object_pattern">null
+ * object pattern</a> for the attached mvp view. So whenever the view gets detached from this
+ * presenter by calling{@link #detachView(boolean)}, a new "null object" view gets dynamically
+ * instantiated by using reflections and set as the current
+ * view (instead of null). The new "null object" view simply does nothing. This avoids null pointer
+ * exceptions and checks like {@code if (getView() != null)}
+ *
+ * @param <V> The type of the {@link MvpView}
+ * @author Jens Dirller , Hannes Dorfmann
+ * @see MvpBasePresenter
+ * @since 1.2.0
+ */
 public class MvpNullObjectBasePresenter<V extends MvpView> implements MvpPresenter<V> {
 
   private V view;
 
-  @Override
-  public void attachView(V view) {
+  @Override public void attachView(V view) {
     this.view = view;
   }
 
@@ -16,8 +28,7 @@ protected V getView() {
     return view;
   }
 
-  @Override
-  public void detachView(boolean retainInstance) {
+  @Override public void detachView(boolean retainInstance) {
     if (view != null) {
       //noinspection unchecked
       Class<V> viewClass = (Class<V>) view.getClass().getGenericInterfaces()[0];

mvp-common/src/main/java/com/hannesdorfmann/mosby/mvp/NoOp.java

@@ -1,3 +1,20 @@
+/*
+ *  Copyright 2015. Hannes Dorfmann.
+ *
+ * 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 com.hannesdorfmann.mosby.mvp;
 
 import java.lang.reflect.InvocationHandler;
@@ -6,6 +23,12 @@
 import static com.hannesdorfmann.mosby.mvp.Defaults.defaultValue;
 import static java.lang.reflect.Proxy.newProxyInstance;
 
+/**
+ * Dynamically proxy to generate a new object instance for a given class by using reflections
+ *
+ * @author Jens Dirller
+ * @since 1.2.0
+ */
 final class NoOp {
 
   private static final InvocationHandler DEFAULT_VALUE = new DefaultValueInvocationHandler();
@@ -14,15 +37,14 @@ private NoOp() {
     // no instances
   }
 
-  @SuppressWarnings("unchecked")
-  public static <T> T of(Class<T> interfaceClass) {
-    return (T) newProxyInstance(interfaceClass.getClassLoader(), new Class[] { interfaceClass }, DEFAULT_VALUE);
+  @SuppressWarnings("unchecked") public static <T> T of(Class<T> interfaceClass) {
+    return (T) newProxyInstance(interfaceClass.getClassLoader(), new Class[] { interfaceClass },
+        DEFAULT_VALUE);
   }
 
   private static class DefaultValueInvocationHandler implements InvocationHandler {
 
-    @Override
-    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+    @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
       return defaultValue(method.getReturnType());
     }
   }

mvp-common/src/test/java/com/hannesdorfmann/mosby/mvp/MvpNullObjectBasePresenterTest.java

@@ -0,0 +1,93 @@
+/*
+ *  Copyright 2015. Hannes Dorfmann.
+ *
+ * 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 com.hannesdorfmann.mosby.mvp;
+
+import java.util.Date;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * @author Hannes Dorfmann
+ */
+public class MvpNullObjectBasePresenterTest {
+
+  public interface TestView extends MvpView {
+    public void showFoo(TestData data);
+
+    public void showThat();
+  }
+
+  public class TestData {
+    int a;
+    String b;
+    Date date = new Date();
+  }
+
+  public class TestNullObjectPresenter
+      extends MvpNullObjectBasePresenter<MvpNullObjectBasePresenterTest.TestView> {
+
+    public void viewShowFoo(TestData data) {
+      getView().showFoo(data);
+    }
+
+    public void viewShowThat() {
+      getView().showThat();
+    }
+  }
+
+  @Test public void testAttachDetach() {
+
+    TestNullObjectPresenter presenter = new TestNullObjectPresenter();
+
+    try {
+      // NullPointer exception should be thrown
+      presenter.getView();
+      Assert.fail("Nullpointer Exception should be thrown but haven't");
+    } catch (NullPointerException e) {
+      // Expected exception
+    }
+
+    TestView view = new TestView() {
+      @Override public void showFoo(TestData data) {
+      }
+
+      @Override public void showThat() {
+      }
+    };
+
+    presenter.attachView(view);
+    Assert.assertNotNull(presenter.getView());
+    Assert.assertTrue(presenter.getView() == view);
+
+    // Test with retainInstance == false
+    presenter.detachView(false);
+    Assert.assertNotNull(presenter.getView());
+    Assert.assertTrue(presenter.getView() != view); // Null Object view
+
+    // Reattach real view
+    presenter.attachView(view);
+    Assert.assertNotNull(presenter.getView());
+    Assert.assertTrue(presenter.getView() == view);
+
+    // Test with retainInstance == true
+    presenter.detachView(true);
+    Assert.assertNotNull(presenter.getView());
+    Assert.assertTrue(presenter.getView() != view); // Null Object view
+  }
+
+}