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Refactoring Wunderlist for Android César Valiente - Episode I. The presentation layer -

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Who is this guy? Image Placeholder César Valiente Android Engineer @Wunderlist (@Microsoft) Android Google Developer Expert (GDE) +CesarValiente @CesarValiente

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This is a story of…

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evolution

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growth evolution

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growth simplicity evolution

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growth simplicity evolution improvement

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How is Wunderlist built?

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How is Wunderlist built? Android Layer Presentation layer (UI and Android stuff) Android project

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How is Wunderlist built? Android Layer Presentation layer (UI and Android stuff) Android project Sync Layer Model layer (Business logic) Java project

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How is Wunderlist built? Android Layer Presentation layer (UI and Android stuff) Android project Sync Layer Model layer (Business logic) Java project Network Layer Network layer (Accessing to the API data) Java project

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How is Wunderlist built? Android Layer Presentation layer (UI and Android stuff) Android project Sync Layer Model layer (Business logic) Java project Network Layer Network layer (Accessing to the API data) Java project Sync boundaries

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How is Wunderlist built? Android Layer Presentation layer (UI and Android stuff) Android project Sync Layer Model layer (Business logic) Java project Network Layer Network layer (Accessing to the API data) Java project Sync boundaries Network boundaries

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Dependency rule

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Network Dependency rule

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Sync Network Dependency rule

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Presentation Sync Network Dependency rule

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Presentation Sync Network Dependency rule The outer model knows the inner, not viceversa.

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Problems?

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Problems? Activities/Fragments become GOD classes.

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Problems? Activities/Fragments become GOD classes. Responsibilities are messed up.

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Problems? Activities/Fragments become GOD classes. Responsibilities are messed up. Database in presentation layer (since it was our only Android related layer).

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Problems? Activities/Fragments become GOD classes. Responsibilities are messed up. Difficult to test: framework dependencies. Database in presentation layer (since it was our only Android related layer).

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Problems? Activities/Fragments become GOD classes. Responsibilities are messed up. Difficult to test: framework dependencies. Database in presentation layer (since it was our only Android related layer). Cache in the sync layer.

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Problems? Activities/Fragments become GOD classes. Responsibilities are messed up. Difficult to test: framework dependencies. Database in presentation layer (since it was our only Android related layer). Cache in the sync layer. Complex data schemes used also in the presentation layer, not needed here.

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Problems? Activities/Fragments become GOD classes. Responsibilities are messed up. Difficult to test: framework dependencies. Database in presentation layer (since it was our only Android related layer). Cache in the sync layer. Complex data schemes used also in the presentation layer, not needed here. We wanted to do it better!

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What are we going to do?

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What are we going to do? We are going to separate responsibilities. Yes, Even more!

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What are we going to do? We are going to separate responsibilities. Yes, Even more! We are going to decouple the different core elements of our app.

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What are we going to do? We are going to separate responsibilities. Yes, Even more! We are going to decouple the different core elements of our app. We are going to improve the way we fetch data.

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What are we going to do? We are going to separate responsibilities. Yes, Even more! We are going to decouple the different core elements of our app. We are going to improve the way we fetch data. We are going to make testing easier to do, and increase our test coverage.

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What are we going to do? We are going to separate responsibilities. Yes, Even more! We are going to decouple the different core elements of our app. We are going to improve the way we fetch data. We are going to make testing easier to do, and increase our test coverage. We are going to improve our codebase.

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What are we going to do? We are going to separate responsibilities. Yes, Even more! We are going to REFACTOR We are going to decouple the different core elements of our app. We are going to improve the way we fetch data. We are going to make testing easier to do, and increase our test coverage. We are going to improve our codebase.

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Presentation layer

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Presentation layer App/UI (Android project)

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Presentation layer App/UI (Android project) UI domain (Java project)

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Presentation layer App/UI (Android project) UI domain (Java project) DB/Cache (Android project)

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Everything starts with the Model View Presenter (MVP)

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VIEW Activity/Fragment Everything starts with the Model View Presenter (MVP)

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VIEW Activity/Fragment PRESENTER Man in the middle Everything starts with the Model View Presenter (MVP)

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VIEW Activity/Fragment PRESENTER Man in the middle MODEL Business logic Everything starts with the Model View Presenter (MVP)

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VIEW Activity/Fragment PRESENTER Man in the middle MODEL Business logic User interacts with the app Everything starts with the Model View Presenter (MVP)

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VIEW Activity/Fragment PRESENTER Man in the middle MODEL Business logic Starts the process User interacts with the app Everything starts with the Model View Presenter (MVP)

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VIEW Activity/Fragment PRESENTER Man in the middle MODEL Business logic Starts the process Executes use case User interacts with the app Everything starts with the Model View Presenter (MVP)

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VIEW Activity/Fragment PRESENTER Man in the middle MODEL Business logic Starts the process Executes use case Returns the result User interacts with the app Everything starts with the Model View Presenter (MVP)

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VIEW Activity/Fragment PRESENTER Man in the middle MODEL Business logic Starts the process Executes use case Updates view Returns the result User interacts with the app Everything starts with the Model View Presenter (MVP)

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VIEW PRESENTER

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VIEW PRESENTER VIEWCALLBACK USE CASE

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VIEW PRESENTER VIEWCALLBACK USE CASE implements and passes it to the presenter

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VIEW PRESENTER VIEWCALLBACK USE CASE implements and passes it to the presenter creates an instance and passes it to the presenter

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VIEW PRESENTER VIEWCALLBACK USE CASE implements and passes it to the presenter creates an instance and passes it to the presenter will execute it to start the process

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VIEW PRESENTER VIEWCALLBACK USE CASE implements and passes it to the presenter creates an instance and passes it to the presenter will invoke it to communicate back (when we have the result) will execute it to start the process

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ViewCallback

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public interface ViewCallback {
 void showProgressDialog();
 void hideProgressDialog();
 void updateList(List content);
 }

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View

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public class SharingFragmentActivity extends WLFragmentActivity implements ViewCallback {

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private View progressDialog;
 private Adapter adapter;
 private SharingPresenter sharingPresenter;
 
 public void onCreate (Bundle onSavedInstanceState) {
 super.onCreate(onSavedInstanceState);
 
 bindViews();
 setupPresenters();
 } public class SharingFragmentActivity extends WLFragmentActivity implements ViewCallback {

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private View progressDialog;
 private Adapter adapter;
 private SharingPresenter sharingPresenter;
 
 public void onCreate (Bundle onSavedInstanceState) {
 super.onCreate(onSavedInstanceState);
 
 bindViews();
 setupPresenters();
 } public class SharingFragmentActivity extends WLFragmentActivity implements ViewCallback { private void setupPresenters () {
 GetListMembershipUseCase getListMembershipUseCase = new GetListMembershipUseCase( listId, appDataController); sharingPresenter = new SharingPresenter ( this, getListMembershipUseCase);
 } //——————— next slides ———————//

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public class SharingFragmentActivity extends WLFragmentActivity implements ViewCallback { //——————————-— previous slide (setup) ———————————-—// //——————— next slide (presenter invocation) ———————//

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@Override void showProgressDialog() {
 progressDialog.show();
 }
 
 @Override void hideProgressDialog() {
 progressDialog.hide();
 }
 
 @Override void updateList(List list) {
 adapter.updateContent(list);
 }
 } public class SharingFragmentActivity extends WLFragmentActivity implements ViewCallback { //——————————-— previous slide (setup) ———————————-—// //——————— next slide (presenter invocation) ———————// implements ViewCallback {

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//——————————— slide 1 (setup) —————————-—// public class SharingFragmentActivity extends WLFragmentActivity implements ViewCallback { //————— slide 2 (ViewCallback impl) ————-//

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@OnClick private void showListMembers () {
 sharingPresenter.getListMembers();
 } //——————————— slide 1 (setup) —————————-—// public class SharingFragmentActivity extends WLFragmentActivity implements ViewCallback { //————— slide 2 (ViewCallback impl) ————-//

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Presenter

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public class SharingPresenter extends Presenter {

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public class SharingPresenter extends Presenter { private ViewCallback viewCallback;
 private GetListMembershipUseCase getListMembershipUseCase;
 
 public SharingPresenter ( ViewCallback viewCallback, GetListMembershipUseCase getListMembershipUseCase) { 
 this.viewCallback = viewCallback;
 this.getListMembershipUseCase = getListMembershipUseCase;
 } //——————— next slides ———————//

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public class SharingPresenter extends Presenter { //——————————-— previous slide (setup) ———————————-—//

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@Override public void onStart() {
 EventBus.getDefault().register(this);
 }
 
 @Override public void onStop() {
 EventBus.getDefault().unregister(this);
 } public class SharingPresenter extends Presenter { //——————————-— previous slide (setup) ———————————-—//

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@Override public void onStart() {
 EventBus.getDefault().register(this);
 }
 
 @Override public void onStop() {
 EventBus.getDefault().unregister(this);
 } public class SharingPresenter extends Presenter { //——————————-— previous slide (setup) ———————————-—// public void onEventMainThread(ListMembershipEvent event) {
 viewCallback.hideProgressDialog();
 viewCallback.updateList(event.getContent());
 } //——————— next slide (Use Case execution) ———————//

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public class SharingPresenter extends Presenter { //————————————- slide 1 (setup) ———————————————————-—// //———————————— slide 2 (listening for events) ———————//

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public void showListMembers () {
 viewCallback.showProgressDialog();
 getListMembershipUseCase.execute();
 }
 } public class SharingPresenter extends Presenter { //————————————- slide 1 (setup) ———————————————————-—// //———————————— slide 2 (listening for events) ———————//

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No content

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M O D E L

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M O D E L Use Cases

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UI-Items, DB, Cache, etc. M O D E L Use Cases

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Use case

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public class GetListMembershipUseCase implements UseCase> {

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public class GetListMembershipUseCase implements UseCase> { private String listId;
 private AppDataController appDataController;
 
 public GetListUseCase( String listId, AppDataController appDataController) {
 this.listId = listId;
 this.appDataController = appDataController;
 }
 


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public class GetListMembershipUseCase implements UseCase> { private String listId;
 private AppDataController appDataController;
 
 public GetListUseCase( String listId, AppDataController appDataController) {
 this.listId = listId;
 this.appDataController = appDataController;
 }
 
 @Override
 public void execute() {
 appDataController.get(ApiObjectType.MEMBERSHIP, listId);
 }
 }

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How were we fetching data?

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LOADER Activity/ Fragment DB Presentation layer 1. Using loaders

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LOADER Activity/ Fragment DB Presentation layer 1. Using loaders

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LOADER Activity/ Fragment DB Presentation layer 1. Using loaders

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LOADER Activity/ Fragment BUS Event or data is fired Presentation layer 2. Using loaders + Bus

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LOADER Activity/ Fragment BUS Subscription Event or data is fired Presentation layer 2. Using loaders + Bus

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LOADER Activity/ Fragment BUS Subscription Event or data is fired Data Presentation layer 2. Using loaders + Bus

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LOADER Activity/ Fragment BUS Subscription Data Event or data is fired Data Presentation layer 2. Using loaders + Bus

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And how do we fetch data now? (an evolution of approaches)

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1. Use case that returns data. Synchronous. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e

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1. Use case that returns data. Synchronous. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1

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1. Use case that returns data. Synchronous. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2

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1. Use case that returns data. Synchronous. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 3

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1. Use case that returns data. Synchronous. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 3 4

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1. Use case that returns data. Synchronous. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 5 3 4

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1. Use case that returns data. Synchronous. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 5 6 3 4

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2. Use case using callback. Asynchronous. 2 Presenter View Presentation layer Model UI domain db/ cache U s e C a s e

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2. Use case using callback. Asynchronous. 2 Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1

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2. Use case using callback. Asynchronous. 2 Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2

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2. Use case using callback. Asynchronous. 2 Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 3

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2. Use case using callback. Asynchronous. 2 Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 3 4

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2. Use case using callback. Asynchronous. 2 Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 5 3 4

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2. Use case using callback. Asynchronous. 2 Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 5 6 3 4

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3. Use case using an event bus. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e BUS

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3. Use case using an event bus. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 BUS

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3. Use case using an event bus. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 BUS

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3. Use case using an event bus. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 BUS 3

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3. Use case using an event bus. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 BUS 3 4

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3. Use case using an event bus. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 BUS 3 4 5

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3. Use case using an event bus. Presenter View Presentation layer Model UI domain db/ cache U s e C a s e 1 2 6 BUS 3 4 5

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4. Use case using RxJava Model UI domain db/ cache OBSERVABLE Presentation layer VIEW PRESENTER OBSERVER (USE CASE)

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4. Use case using RxJava Model UI domain db/ cache OBSERVABLE Presentation layer VIEW PRESENTER OBSERVER 1 (USE CASE)

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4. Use case using RxJava Model UI domain db/ cache OBSERVABLE Presentation layer VIEW PRESENTER OBSERVER 1 2 (USE CASE)

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4. Use case using RxJava Model UI domain db/ cache OBSERVABLE Presentation layer VIEW PRESENTER OBSERVER 3 1 2 (USE CASE)

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4. Use case using RxJava Model UI domain db/ cache OBSERVABLE Presentation layer VIEW PRESENTER OBSERVER 3 4 1 2 (USE CASE)

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4. Use case using RxJava Model UI domain db/ cache OBSERVABLE Presentation layer VIEW PRESENTER OBSERVER 5 3 4 1 2 (USE CASE)

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4. Use case using RxJava Model UI domain db/ cache OBSERVABLE Presentation layer 6 VIEW PRESENTER OBSERVER 5 3 4 1 2 (USE CASE)

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Testing?

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Testing? Views now don’t have business logic and/or data.

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Testing? Views now don’t have business logic and/or data. Presenters don’t have framework dependencies.

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Testing? Views now don’t have business logic and/or data. Presenters don’t have framework dependencies. Dependency injection make testing easier

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Testing? Views now don’t have business logic and/or data. Presenters don’t have framework dependencies. Use cases are very small and simple. Dependency injection make testing easier

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Testing? Views now don’t have business logic and/or data. Presenters don’t have framework dependencies. Use cases are very small and simple. We can test now every component independently. Dependency injection make testing easier

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Testing? Views now don’t have business logic and/or data. Presenters don’t have framework dependencies. Use cases are very small and simple. We can test now every component independently. Dependency injection make testing easier Now testing is easy peasy!

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More testing?

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More testing? VIEW Espresso Java + Android Mockito JUnit

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More testing? VIEW Espresso Java + Android Mockito JUnit PRESENTER TestSubscriber Mockito JUnit Java + RxJava

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More testing? VIEW Espresso Java + Android Mockito JUnit PRESENTER TestSubscriber Mockito JUnit Java + RxJava USE CASE TestSubscriber Mockito JUnit Java + RxJava

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More testing? VIEW Espresso Java + Android Mockito JUnit PRESENTER TestSubscriber Mockito JUnit Java + RxJava USE CASE TestSubscriber Mockito JUnit Java + RxJava UI- DOMAIN TestSubscriber Mockito JUnit Java + RxJava

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More testing? VIEW Espresso Java + Android Mockito JUnit PRESENTER TestSubscriber Mockito JUnit Java + RxJava USE CASE TestSubscriber Mockito JUnit Java + RxJava UI- DOMAIN TestSubscriber Mockito JUnit Java + RxJava DB/ CACHE Java + Android + RxJava Robolectric Mockito JUnit TestSubscriber

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Lessons learned

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Lessons learned Dependency Inversion Principle is key.

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Lessons learned Dependency Inversion Principle is key. Following SOLID principles makes MVP easy to build.

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Lessons learned Dependency Inversion Principle is key. Following SOLID principles makes MVP easy to build. Small use cases define what you want to do.

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Lessons learned Dependency Inversion Principle is key. Following SOLID principles makes MVP easy to build. Small use cases define what you want to do. We have different alternatives to fetch data, choose yours.

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Lessons learned Dependency Inversion Principle is key. Following SOLID principles makes MVP easy to build. Small use cases define what you want to do. We have different alternatives to fetch data, choose yours. Decouple components makes testing easier.

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? +CesarValiente @CesarValiente

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+CesarValiente @CesarValiente Thanks!

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License (cc) 2016 César Valiente. Some rights reserved. This document is distributed under the Creative Commons Attribution-ShareAlike 3.0 license, available in http://creativecommons.org/licenses/by-sa/3.0/

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Image licenses Wunderlist (Microsoft): permission granted. Emojis by Emoji One (CC-BY): http://emojione.com/ Iceberg: http://science-all.com/iceberg.html All images belong to their owners.