From Legacy to Hexagonal (Codemotion Madrid 2014)

Transcript

1. From Legacy to Hexagonal (An Unexpected Android Journey) Rubén Serrano @Akelael Lead Android Developer @RedboothHQ José Manuel Pereira @JMPergar Android Software Engineer @RedboothHQ
2. Agenda 1. From Legacy Code 2. Towards Hexagonal Architecture 3. To infinity, and beyond!
3. 1. From Legacy Code
4. Meet the team
7. One dev from a contractor
8. One dev from a contractor + one senior iOS dev
9. One dev from a contractor + one senior iOS dev
10. One dev from a contractor + one senior iOS dev + one junior iOS dev
11. One dev from a contractor + one senior iOS dev + one junior iOS dev
12. A different Android dev One dev from a contractor + one senior iOS dev + one junior iOS dev
13. A different Android dev One dev from a contractor + one senior iOS dev + one junior iOS dev + one confused Android team
14. Meet the code
16. Meet the problem
17. 1. We have a huge technical debt
18. 1. We have a huge technical debt
19. HUGE
21. 1. We have huge technical debt 2. We can’t stop developing new features
22. 1. We have huge technical debt 2. We can’t stop developing new features 3. We can’t remove debt at this point and we shouldn’t add any more
23. 2. Towards Hexagonal
24. Working with legacy code
25. Read this book
26. What have we learnt from pizza?
27. You just don’t eat the whole pizza at once
28. 1. Slice the big methods into small meaningful methods
29. 1. Slice the big methods into small meaningful methods 2. Identify different responsibilities and move them to other classes
30. 1. Slice the big methods into small meaningful methods 2. Identify different responsibilities and move them to other classes 3. Use less coupled framework components (or no components at all)
31. Model View Presenter
32. In theory
33. View Presenter Model
34. Notifies events View Presenter Model
35. Requests data View Presenter Model
36. Serves data View Presenter Model
37. Change data representation View Presenter Model
38. Tells how to draw View Presenter Model
39. Layout + Activity/ Fragment Presenter Data + Business logic
40. In code (Original code…) http://goo.gl/z5Xn2J
41. listAdapter =
 new SimpleCursorAdapter(getActivity(),
 android.R.layout.simple_list_item_1,
 null,
 new String[]{FakeDatabase.COLUMN_NAME},
 new int[]{android.R.id.text1},
 0);
 listView.setAdapter(listAdapter); MainFragment
42. 
 getLoaderManager().initLoader(0, null, new LoaderManager.LoaderCallbacks<Cursor>() {
 @Override
 public Loader<Cursor> onCreateLoader(int id, Bundle args) {
 return new CursorLoader(getActivity(), MainContentProvider.URI, null, null, null, null);
 }
 
 @Override
 public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
 listAdapter.swapCursor(data);
 }
 
 @Override
 public void onLoaderReset(Loader<Cursor> loader) {
 listAdapter.swapCursor(null);
 }
 }); MainFragment
43. In Code (… to MVP) http://goo.gl/Retvli
44. MainView & MainModel public interface MainView {
 public void swaplListData(Cursor cursor);
 } public interface MainModel {
 public void setPresenter(MainPresenter presenter);
 public void startLoadingData(Context context);
 }
45. MainFragment public class MainFragment extends Fragment implements MainView {
 //...
 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 presenter = PresenterFactory.getMainPresenter(this);
 } @Override
 public void onActivityCreated(Bundle savedInstanceState) {
 //...
 presenter.notifyOnCreate(getActivity());
 } @Override
 public void swaplListData(Cursor cursor) {
 listAdapter.swapCursor(cursor);
 }
46. MainPresenter public class MainPresenter {
 private MainView mainView;
 private MainModel mainModel;
 
 //...
 
 public void notifyOnCreate(Context context) {
 mainModel.startLoadingData(context);
 }
 
 public void notifiyLoadedDataAvailable(Cursor cursor) {
 mainView.swaplListData(cursor);
 }
 }
47. PresenterFactory public class PresenterFactory {
 public static MainPresenter getMainPresenter(MainView view) {
 MainModel model = new MainCursorModel();
 return MainPresenter.newInstance(view, model);
 }
 }
48. MainCursorModel public class MainCursorModel implements MainModel {
 //... 
 @Override
 public void startLoadingData(Context context) {
 new LoadDataAsyncTask().execute(context);
 }
 
 private class LoadDataAsyncTask extends AsyncTask<Context, Void, Cursor > {
 //... 
 @Override
 protected void onPostExecute(Cursor result) {
 super.onPostExecute(result);
 presenter.notifiyLoadedDataAvailable(result);
 }
 }
 }
49. Pros & Cons View decoupled from model Cleaner code and smaller fragment/activities View and model not really decoupled (cursor) All the components use the framework
50. Hexagonal Architecture
51. In theory
52. Layout + Activity/ Fragment Presenter Data + Business logic
53. Layout + Activity/ Fragment Data domain Business logic
54. Layout + Activity/ Fragment Database Business logic Network Sensors
55. Sensors Network Database Layout + Activity/ Fragment Business logic
56. Business logic Sensors Network Database Layout + Activity/ Fragment
57. Business logic Port Port Port Port Sensors Network Database Layout + Activity/ Fragment
58. Sensors Network Database Layout + Activity/ Fragment Adapter Adapter Adapter Adapter Business logic Port Port Port Port
59. Sensors Network Database Layout + Activity/ Fragment Adapter Adapter Adapter Adapter Business logic Port Port Port Port
60. Sensors Network Database Layout + Activity/ Fragment Boundary Boundary Boundary Boundary Business logic Port Port Port Port
61. Module Core Module App Module App Module App Module App Core Core Core Core App App App App
62. In code (Hexagonal) http://goo.gl/lIyH0o
63. MainFragment public class MainFragment extends Fragment {
 //...
 private MainFragmentBoundary viewBoundary;
 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 //...
 viewBoundary = MainFragmentBoundary.newInstance(this);
 }
 
 @Override
 public void onActivityCreated(Bundle savedInstanceState) {
 //...
 viewBoundary.notifyOnCreate();
 }
64. MainFragment public void setListAdapter() {
 listAdapter = new ArrayAdapter<String>(getActivity(),
 android.R.layout.simple_list_item_1,
 android.R.id.text1,
 new ArrayList<String>(0));
 listView.setAdapter(listAdapter);
 }
 
 public void swapList(List<String> names) {
 listAdapter.clear();
 listAdapter.addAll(names);
 }
65. MainFragmentBoundary public class MainFragmentBoundary implements MainViewPort {
 private MainFragment mainFragment;
 private MainLogic logic;
 
 //...
 public void notifyOnCreate() {
 logic.notifyOnCreate();
 } 
 @Override
 public void swaplListData(List<String> names) {
 mainFragment.swapList(names);
 }
66. MainModelBoundary public class MainModelBoundary implements MainModelPort {
 private MainLogic logic;
 private MainRepository repository;
 //...
 
 @Override
 public void startLoadingData() {
 repository.startLoadingData(new MainRepository.OnDataLoadedListener() {
 @Override
 public void onDataLodaded(Cursor cursor) {
 notifyDataLoaded(cursor);
 }
 });
 }
 
 private void notifyDataLoaded(Cursor cursor) {
 List<String> names = mapCursorToList(cursor);
 logic.notifiyLoadedDataAvailable(names);
 }
67. MainModelBoundary private List<String> mapCursorToList(Cursor cursor) {
 List<String> names = new ArrayList<String>();
 int nameColumnIndex = cursor.getColumnIndex(FakeDatabase.COLUMN_NAME);
 while (cursor.moveToNext()) {
 String name = cursor.getString(nameColumnIndex);
 names.add(name);
 }
 return names;
 }
68. Pros & Cons Logic is not going to be affected by framework changes Logic is pure Java: easier to test Less changes when replacing a plugin Easier for 2 devs to work on the same feature More complex architecture Need to map each POJO for each layer What happens when the plugins need to cooperate?
69. 3. To infinity, and beyond!
70. One plugin, N commands
71. Sensors Network Database Layout + Activity/ Fragment Boundary Boundary Boundary Boundary Business logic Port Port Port Port
72. Model Plugin Layout + Activity/ Fragment Boundary Boundary Business logic Port Port
73. Create task Send chat message Update note Request projects Business logic Port Model Plugin Boundary
74. Asynchrony?
75. Create task Send chat message Update note Request projects Business logic Port Model Plugin Boundary
76. We don’t like: callback’s hell + AsyncTasks
77. We don’t like: callback’s hell + AsyncTasks We don’t mind (but could be a problem): only commands in separate threads
78. We don’t like: callback’s hell + AsyncTasks We don’t mind (but could be a problem): only commands in separate threads We would love: RxJava
79. Use cases
80. Model Plugin Layout + Activity/ Fragment Boundary Boundary Business logic Port Port
81. Model Plugin Layout + Activity/ Fragment Presenter Use Case Model Plugin Use Case Repository Model Plugin Use Case
82. Conclusions photo by Daniel Sancho
83. When? • If you expect 2+ devs working on the same feature • Unless you are sure the app is going to die in a near future • You know for sure you will change your plugins
84. How? 1. Simple refactors 2. Model View Presenter 3. Hexagonal
85. How? 1. Simple refactors 2. Model View Presenter 3. Hexagonal 4. Clean Architecture
86. Thank you!
87. Questions?