Refactoring Plaid - A Reactive MVP Approach

Nick Butcher, developer advocate at Google, has open sourced an android app called Plaid with an outstanding UI, meaningful animations and a lot of others material design goodies.

However, from the software architecture’s point of view, the architecture of this app more “traditional” so that both, beginners and expert developers, can understand the source code easily. Unfortunately, that means that there is a lack of separation of concerns that modern software architectures offers. This talk discusses how to improve the architecture of this app by applying Model-View-Presenter (MVP) to create modular and decoupled components that are easy to test. Furthermore, this talk shows how to improve the code quality by using well known libraries like RxJava (foreknowledge is not a strong requirement), dependency injection and how to test such an App by doing Test-Driven-Development (TDD) from the very beginning.

The aim of this talk is to showcase the importance of a well thought out software architecture and how to implement such an MVP based architecture and last but not least to clarify what the word “reactive” actually means in this context.

YouTube Video: https://youtu.be/wWyPc_HN77c

Transcript

3. HELLO I’m Hannes
4. REFACTORING PLAID A REACTIVE MVP APPROACH
5. SLOWED DOWN BY BAD CODE?
6. FEAR CHANGING CODE!
7. FEAR CHANGING CODE!
8. TDD Test-Driven-Development
9. SOLID Robert C. Martins
 „Uncle Bob“
10. SINGLE RESPONSIBILITY “A class should only have one reason to change” Book 
 currentPage() nextPage() print()
11. SINGLE RESPONSIBILITY “A class should only have one reason to change” Book 
 currentPage() nextPage() print() Book 
 currentPage() nextPage() Printer 
 print(Book)
12. IMMUTABILITY
14. You want an 
 immutable hot dog
15. AUTOVALUE @AutoValue public abstract class HotDog { }
16. AUTOVALUE @AutoValue public abstract class HotDog implements Parcelable { }
17. AUTOVALUE @AutoValue public abstract class HotDog implements Parcelable {
 @Json public abstract double getPrice(); }
18. AUTOVALUE @AutoValue public abstract class HotDog implements Parcelable {
 @Json public abstract double getPrice(); @ColumnName public abstract boolean hasKetchup(); }
19. AUTOVALUE @AutoValue public abstract class HotDog implements Parcelable {
 @Json public abstract double getPrice(); @ColumnName public abstract boolean hasKetchup(); public abstract static HotDog(double p, boolean k) { return new AutoValue_HotDog(p, k); } }
20. MVC Model-View-Controller
21. MVC Trygve Reenskaug View Model Controller observes changes
23. PLAID Nick Butcher
25. PLAID • https://github.com/nickbutcher/plaid • 5170 Stars on Github • Last commit: 1st of June 2016 • 5.000 - 10.000 installs 2nd June 2016
32. PLAID • No clear Separation of responsibilities • AsyncTask • Android Services • Shared Preferences for persistency 2nd June 2016
37. HomeActivity
38. HomeActivity
39. HomeActivity ConnectivityManager
40. HomeActivity ConnectivityManager Animations
41. HomeActivity ConnectivityManager Animations FeedAdapter
42. HomeActivity ConnectivityManager Animations FilterAdapter FeedAdapter
43. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter
44. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter
45. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap
46. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged()
47. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged()
48. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged()
49. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged()
50. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged()
51. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged() SourceManager
52. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged() SourceManager
53. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged() SourceManager
54. REFACTORING
55. Internet
56. Mock
57. https://www.getpostman.com/
58. src/test/resources ClassLoader classLoader = getClass().getClassLoader(); File file = new File(classLoader.getResource("somefile.json").getFile());
59. src/test/resources ClassLoader classLoader = getClass().getClassLoader(); File file = new File(classLoader.getResource("somefile.json").getFile()); Mock https://github.com/square/okhttp/tree/master/mockwebserver
60. src/test/resources ClassLoader classLoader = getClass().getClassLoader(); File file = new File(classLoader.getResource("somefile.json").getFile()); Mock https://github.com/square/okhttp/tree/master/mockwebserver @Rule https://github.com/artem-zinnatullin/qualitymatters
61. class HomeActivityTest {
 @Rule MockWebServer server = new MockWebServer(); @Test public void showItems(){ server.enqueue( new MockResponse (…) ); onView( withId( R.id.recyclerView )) .check( matches( isDisplayed() ); onView(withId( R.id.recyclerView)) .check( new RecyclerViewItemCountAssertion(20) ) // test visibility of error and loading view }
62. CLEAN ARCHITECTURE Entity Entity Entity Interactor
 Presenter
 View

63. CLEAN ARCHITECTURE Entity Entity Entity Interactor
 Presenter
 View
 Break the Rules! https://publicobject.com/2016/04/20/deliberate-disobedience/ Jesse Wilson
64. HomeActivity ConnectivityManager Animations onActivityResult() FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap FilterAdapter getFilters() registerFilterChanged() SourceManager
65. HomeActivity Animations FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap SourceManager
66. REACTIVE PROGRAMMING
67. java.util.Observable
68. SQLBrite SQLiteDatabase SourceDao
69. interface SourceDao {
 
 fun getAllSources(): Observable<List<Source>>
 
 fun getEnabledSources(): Observable<List<Source>>
 
 fun insert(source: Source): Observable<Long>
 
 fun delete(source: Source): Observable<Int> }
70. @AutoValue class Source : Parcelable {
 @ColumnName(COL_NAME) fun name() : String @ColumnName(COL_ENABLED) fun boolean enabled(); }
71. TDD • Write failing unit test first • Write just enough code to pass all tests • Repeat
72. class SqliteSourceDaoTest {
 @Test fun insertAndGet(){ dao = SqliteSourceDao() val source = Source.create(…) val inserted = dao.insert(source)
 .toBlocking().first() assertEquals(1, insertRes) } }
73. Unit Test failed
74. class SqliteSourceDao : SourceDao, Dao() {
 
 fun insert(source: Source): Observable<Long> = insert(TABLE, source.toContentValues()) }
75. Unit Tests OK
76. class SqliteSourceDaoTest {
 @Test fun insertAndGet(){ dao = SqliteSourceDao() val source = Source.create(…) val inserted = dao.insert(source)
 .toBlocking().first() assertEquals(1, insertRes) val queried = dao.getAllSources().toBlocking() assertEquals(queried, listOf(source)) } }
77. Unit Test failed
78. class SqliteSourceDao : SourceDao, Dao() {
 
 fun insert(source: Source): Observable<Long> = insert(TABLE, source.toContentValues()) fun getAll(source: Source): Observable<List<Source>> = query( SELECT(“*“).FROM(TABLE) ) .mapToList(Source.MAPPER) }
79. Unit Tests OK
80. HomeActivity Animations FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap SourceManager
81. HomeActivity Animations FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap SourceDao
82. HomeActivity Animations FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap SourceDao
83. HomeActivity Animations FilterAdapter FeedAdapter DataManager pageIndexMap runningCallsMap SourceDao
87. RxBus
88. RxBus
89. HomeActivity Animations FilterAdapter FeedAdapter DataManager SourceDao P R E
 S
 E
 N
 T
 E R
 View Model
90. TESTING MVP • View with Mock Presenter • Presenter with Mock View and Mock Model • Model plain old unit test (slides before)
91. SINGLE RESPONSIBILITY DataManager pageIndexMap runningCallsMap SourceDao
92. SINGLE RESPONSIBILITY DataManager pageIndexMap runningCallsMap SourceDao Route
93. SINGLE RESPONSIBILITY DataManager pageIndexMap runningCallsMap SourceDao Route Queries Http Endpoint
94. SINGLE RESPONSIBILITY DataManager pageIndexMap runningCallsMap SourceDao Route Router Queries Http Endpoint
95. SINGLE RESPONSIBILITY DataManager pageIndexMap runningCallsMap SourceDao Route Router Queries Http Endpoint A collection of Routes
96. SINGLE RESPONSIBILITY DataManager pageIndexMap runningCallsMap SourceDao Route Router Page Queries Http Endpoint A collection of Routes
97. SINGLE RESPONSIBILITY DataManager pageIndexMap runningCallsMap SourceDao Route Router Page Queries Http Endpoint A collection of Routes Page Index
98. OBSERVABLE STREAM SourceDao Route Router Page SQLBrite SQLiteDatabase
99. OBSERVABLE STREAM SourceDao Route Router Page SQLBrite SQLiteDatabase
100. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
101. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
102. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
103. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
104. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
105. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
106. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
107. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
108. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
109. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
110. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
111. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
112. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
113. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
114. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
115. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
116. SourceDao Route Router Page SQLBrite SQLiteDatabase SourceDao HomePresenter HomeActivity FilterPresenter FilterFragment
117. UNIDIRECTIONAL DATAFLOW
119. HomePresenter HomeActivity FilterPresenter FilterFragment SearchPresenter SearchActivity SettingsPresenter SettingsActivity
121. MOVE FAST WITHOUT FEARING TO BREAK THINGS
122. THE CODE YOU WRITE TODAY WILL BE LEGACY CODE TOMORROW
123. JUST LIKE TODAY’S CELLS IN YOUR BODY ARE LEGACY CELLS TOMORROW
124. We are hiring! www.tickaroo.com
125. QUESTIONS? hannesdorfmann.com @sockeqwe