Model View Intent - An Introduction

Transcript

1. Model View Intent An Introduction
2. Jossi Wolf Android Developer About Me
3. MVI MVP MVC MVVM Redux Flux God-like Activities
4. Model View Intent
6. A B C data data Unidirectional Data Flow D data data
7. A B C data data Unidirectional Data Flow D data data
8. someModel.set(…) Immutability
9. someModel.set(…) Immutability
10. String calendar = "calendar"; System.out.println(calendar.toUpperCase()); // CALENDAR Pure Functions
11. public class SchoolsViewState { boolean loading; Throwable error; List<SchoolsModel> schools; } State Model
12. Data Flow in MVI View Intents (User Actions) Business Logic emits Presenter Model
13. public interface SchoolsViewPresenterContract { interface SchoolsViewActions { } interface SchoolsPresenterActions { } }
14. interface SchoolsPresenterActions { void loadSchools(); }
15. interface SchoolsViewActions { void showLoading(); void showSuccess(); void showError(); }
16. interface SchoolsViewActions { void render(SchoolsViewState state); }
17. public class SchoolsActivity implements SchoolsViewActions { @Override public void render(SchoolsViewState state) { // The view decides how to render the state } }
18. @Override public void render(SchoolsViewState state) { if (state.getError() != null) { showError(state.getError().getMessage()); } if (state.isLoading()) { showLoader(); clearAdapter(); } else if (!state.isLoading()) { hideLoader(); } if (state.getSchools() != null) { showSchools(state.getSchools()); } }
19. public class ExampleStateModel { private boolean loading; private Throwable error; private List<SchoolsModel> data; ExampleStateModel(boolean loading, Throwable error, List<SchoolsModel> data) { // set everything } }
20. public class ExampleStateModel { private boolean loading; private Throwable error; private List<SchoolsModel> data; private ExampleStateModel( boolean loading, Throwable error, List<SchoolsModel> data) { // set everything } }
21. public static SchoolsViewState LoadingState() { return new SchoolsViewState(true, null, null); } public static SchoolsViewState ErrorState(Throwable error) { return new SchoolsViewState(false, error, null); } public static SchoolsViewState DataLoadedState(List<SchoolsModel> schools) { return new SchoolsViewState(false, null, schools); }
22. State Reducer
23. HomeViewState { loading = false error = null data = […] }
24. HomeViewState { loading = false error = null data = [a, b, c] } HomeViewState { loading = false error = null data = [x, y, z] } [a, b, c, x, y, z]
25. @Test public void loadSchoolsSuccessful() { when(api.getHamburgSchools()) .thenReturn(Observable.just(generateFakeList())); schoolsPresenter.loadSchools(); verify(schoolsView).render(SchoolsViewState.LoadingState()); verify(schoolsView).render(SchoolsViewState.DataLoadedState(generateFakeList())); }
26. @Test public void loadSchoolsNotSuccessful() { Throwable throwable = new Throwable(); when(api.getHamburgSchools()) .thenReturn(Observable.error(throwable)); schoolsPresenter.loadSchools(); verify(schoolsView).render(SchoolsViewState.LoadingState()); verify(schoolsView).render(SchoolsViewState.ErrorState(throwable)); }
27. Predictability = = + ?
28. Predictability = = =
29. Predictability LoadingState DataLoadedState ErrorState
30. Readable Code Presenter View Interactor Database Network void a( ) void b( )
32. Reading on https://github.com/jossiwolf/MVI-Example https://www.youtube.com/watch?v=0IKHxjkgop4 http://hannesdorfmann.com/android/mosby3-mvi-1 https://github.com/oldergod/android-architecture
33. public MainViewState reduce(MainViewState previous, MainViewState next) { MainViewState computedViewState = MainViewState.Companion.ErrorState(new Throwable("No State")); if (next.getLoading()) { computedViewState = MainViewState.Companion.LoadingState(); } else if (next.getError() != null) { computedViewState = MainViewState.Companion.ErrorState(next.getError()); } else if (next.getData() != null) { List<String> data = new ArrayList<>(); if (previous.getData() != null) { data.addAll(previous.getData()); } data.addAll(next.getData()); computedViewState = MainViewState.Companion.DataLoadedState(data); } return computedViewState; }