Generic use cases

data/src/test/java/com/fernandocejas/android10/sample/data/repository/UserDataRepositoryTest.java

@@ -24,9 +24,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import org.junit.Before;
-import org.junit.Rule;
 import org.junit.Test;
-import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
@@ -48,14 +46,9 @@ public class UserDataRepositoryTest {
   @Mock private UserEntity mockUserEntity;
   @Mock private User mockUser;
 
-  @Rule
-  public ExpectedException expectedException = ExpectedException.none();
-
   @Before
   public void setUp() {
-    userDataRepository = new UserDataRepository(mockUserDataStoreFactory,
-        mockUserEntityDataMapper);
-
+    userDataRepository = new UserDataRepository(mockUserDataStoreFactory, mockUserEntityDataMapper);
     given(mockUserDataStoreFactory.create(anyInt())).willReturn(mockUserDataStore);
     given(mockUserDataStoreFactory.createCloudDataStore()).willReturn(mockUserDataStore);
   }

domain/src/main/java/com/fernandocejas/android10/sample/domain/interactor/GetUserDetails.java

@@ -19,38 +19,40 @@
 import com.fernandocejas.android10.sample.domain.executor.PostExecutionThread;
 import com.fernandocejas.android10.sample.domain.executor.ThreadExecutor;
 import com.fernandocejas.android10.sample.domain.repository.UserRepository;
-import com.fernandocejas.arrow.annotations.VisibleForTesting;
-import com.fernandocejas.arrow.optional.Optional;
+import com.fernandocejas.arrow.checks.Preconditions;
 import io.reactivex.Observable;
 import javax.inject.Inject;
 
 /**
  * This class is an implementation of {@link UseCase} that represents a use case for
  * retrieving data related to an specific {@link User}.
  */
-public class GetUserDetails extends UseCase {
-
-  public static final String NAME = "userDetails";
-  public static final String PARAM_USER_ID_KEY = "userId";
-
-  @VisibleForTesting
-  static final int PARAM_USER_ID_DEFAULT_VALUE = -1;
+public class GetUserDetails extends UseCase<User, GetUserDetails.Params> {
 
   private final UserRepository userRepository;
 
   @Inject
-  public GetUserDetails(UserRepository userRepository, ThreadExecutor threadExecutor,
+  GetUserDetails(UserRepository userRepository, ThreadExecutor threadExecutor,
       PostExecutionThread postExecutionThread) {
     super(threadExecutor, postExecutionThread);
     this.userRepository = userRepository;
   }
 
-  @Override protected Observable buildUseCaseObservable(Optional<Params> params) {
-    if (params.isPresent()) {
-      final int userId = params.get().getInt(PARAM_USER_ID_KEY, PARAM_USER_ID_DEFAULT_VALUE);
-      return this.userRepository.user(userId);
-    } else {
-      return Observable.empty();
+  @Override Observable<User> buildUseCaseObservable(Params params) {
+    Preconditions.checkNotNull(params);
+    return this.userRepository.user(params.userId);
+  }
+
+  public static final class Params {
+
+    private final int userId;
+
+    private Params(int userId) {
+      this.userId = userId;
+    }
+
+    public static Params forUser(int userId) {
+      return new Params(userId);
     }
   }
 }

domain/src/main/java/com/fernandocejas/android10/sample/domain/interactor/GetUserList.java

@@ -19,17 +19,15 @@
 import com.fernandocejas.android10.sample.domain.executor.PostExecutionThread;
 import com.fernandocejas.android10.sample.domain.executor.ThreadExecutor;
 import com.fernandocejas.android10.sample.domain.repository.UserRepository;
-import com.fernandocejas.arrow.optional.Optional;
 import io.reactivex.Observable;
+import java.util.List;
 import javax.inject.Inject;
 
 /**
  * This class is an implementation of {@link UseCase} that represents a use case for
  * retrieving a collection of all {@link User}.
  */
-public class GetUserList extends UseCase {
-
-  public static final String NAME = "userList";
+public class GetUserList extends UseCase<List<User>, Void> {
 
   private final UserRepository userRepository;
 
@@ -40,7 +38,7 @@ public class GetUserList extends UseCase {
     this.userRepository = userRepository;
   }
 
-  @Override public Observable buildUseCaseObservable(Optional<Params> params) {
+  @Override Observable<List<User>> buildUseCaseObservable(Void unused) {
     return this.userRepository.users();
   }
 }

domain/src/main/java/com/fernandocejas/android10/sample/domain/interactor/UseCase.java

@@ -18,7 +18,6 @@
 import com.fernandocejas.android10.sample.domain.executor.PostExecutionThread;
 import com.fernandocejas.android10.sample.domain.executor.ThreadExecutor;
 import com.fernandocejas.arrow.checks.Preconditions;
-import com.fernandocejas.arrow.optional.Optional;
 import io.reactivex.Observable;
 import io.reactivex.disposables.CompositeDisposable;
 import io.reactivex.disposables.Disposable;
@@ -33,7 +32,7 @@
  * By convention each UseCase implementation will return the result using a {@link DisposableObserver}
  * that will execute its job in a background thread and will post the result in the UI thread.
  */
-public abstract class UseCase {
+public abstract class UseCase<T, Params> {
 
   private final ThreadExecutor threadExecutor;
   private final PostExecutionThread postExecutionThread;
@@ -48,18 +47,18 @@ public abstract class UseCase {
   /**
    * Builds an {@link Observable} which will be used when executing the current {@link UseCase}.
    */
-  protected abstract Observable buildUseCaseObservable(Optional<Params> params);
+  abstract Observable<T> buildUseCaseObservable(Params params);
 
   /**
    * Executes the current use case.
    *
    * @param observer {@link DisposableObserver} which will be listening to the observable build
-   * by {@link #buildUseCaseObservable(Optional)} ()} method.
-   * @param params Parameters used to build execute this use case.
+   * by {@link #buildUseCaseObservable(Params)} ()} method.
+   * @param params Parameters (Optional) used to build/execute this use case.
    */
-  @SuppressWarnings("unchecked")
-  public void execute(DisposableObserver observer, Params params) {
-    final Observable<?> observable = this.buildUseCaseObservable(Optional.of(params))
+  public void execute(DisposableObserver<T> observer, Params params) {
+    Preconditions.checkNotNull(observer);
+    final Observable<T> observable = this.buildUseCaseObservable(params)
         .subscribeOn(Schedulers.from(threadExecutor))
         .observeOn(postExecutionThread.getScheduler());
     addDisposable(observable.subscribeWith(observer));

domain/src/test/java/com/fernandocejas/android10/sample/domain/interactor/GetUserDetailsTest.java

@@ -17,16 +17,16 @@
 
 import com.fernandocejas.android10.sample.domain.executor.PostExecutionThread;
 import com.fernandocejas.android10.sample.domain.executor.ThreadExecutor;
+import com.fernandocejas.android10.sample.domain.interactor.GetUserDetails.Params;
 import com.fernandocejas.android10.sample.domain.repository.UserRepository;
-import com.fernandocejas.arrow.optional.Optional;
-import io.reactivex.Observable;
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.verifyZeroInteractions;
@@ -42,6 +42,8 @@ public class GetUserDetailsTest {
   @Mock private ThreadExecutor mockThreadExecutor;
   @Mock private PostExecutionThread mockPostExecutionThread;
 
+  @Rule public ExpectedException expectedException = ExpectedException.none();
+
   @Before
   public void setUp() {
     getUserDetails = new GetUserDetails(mockUserRepository, mockThreadExecutor,
@@ -50,10 +52,7 @@ public void setUp() {
 
   @Test
   public void testGetUserDetailsUseCaseObservableHappyCase() {
-    final Params params = Params.create();
-    params.putInt(GetUserDetails.PARAM_USER_ID_KEY, USER_ID);
-
-    getUserDetails.buildUseCaseObservable(Optional.of(params));
+    getUserDetails.buildUseCaseObservable(Params.forUser(USER_ID));
 
     verify(mockUserRepository).user(USER_ID);
     verifyNoMoreInteractions(mockUserRepository);
@@ -62,22 +61,8 @@ public void testGetUserDetailsUseCaseObservableHappyCase() {
   }
 
   @Test
-  public void testShouldReturnEmptyObservableWhenNoParameters() {
-    final Observable observable = getUserDetails.buildUseCaseObservable(Optional.<Params>absent());
-
-    assertThat(observable).isEqualTo(Observable.empty());
-    verifyZeroInteractions(mockUserRepository);
-    verifyZeroInteractions(mockPostExecutionThread);
-    verifyZeroInteractions(mockThreadExecutor);
-  }
-
-  @Test
-  public void testShouldUseDefaultUserIdValueWhenNoUserIdParameter() {
-    getUserDetails.buildUseCaseObservable(Optional.of(Params.create()));
-
-    verify(mockUserRepository).user(GetUserDetails.PARAM_USER_ID_DEFAULT_VALUE);
-    verifyNoMoreInteractions(mockUserRepository);
-    verifyZeroInteractions(mockPostExecutionThread);
-    verifyZeroInteractions(mockThreadExecutor);
+  public void testShouldFailWhenNoOrEmptyParameters() {
+    expectedException.expect(NullPointerException.class);
+    getUserDetails.buildUseCaseObservable(null);
   }
 }

domain/src/test/java/com/fernandocejas/android10/sample/domain/interactor/GetUserListTest.java

@@ -18,14 +18,12 @@
 import com.fernandocejas.android10.sample.domain.executor.PostExecutionThread;
 import com.fernandocejas.android10.sample.domain.executor.ThreadExecutor;
 import com.fernandocejas.android10.sample.domain.repository.UserRepository;
-import com.fernandocejas.arrow.optional.Optional;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 
-import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.verifyZeroInteractions;
@@ -47,22 +45,11 @@ public void setUp() {
 
   @Test
   public void testGetUserListUseCaseObservableHappyCase() {
-    getUserList.buildUseCaseObservable(Optional.of(Params.EMPTY));
+    getUserList.buildUseCaseObservable(null);
 
     verify(mockUserRepository).users();
     verifyNoMoreInteractions(mockUserRepository);
     verifyZeroInteractions(mockThreadExecutor);
     verifyZeroInteractions(mockPostExecutionThread);
   }
-
-  @Test
-  @SuppressWarnings("unchecked")
-  public void testThereShouldNotBeAnyInteractionWithParams() {
-    Optional params = mock(Optional.class);
-
-    getUserList.buildUseCaseObservable(params);
-
-    verify(mockUserRepository).users();
-    verifyZeroInteractions(params);
-  }
 }