Working with Android legacy code

Transcript

1. Working With Android Legacy Code 2018
2. Daniel Rotenberg Android Developer @ Chegg
3. Chegg is Well-Known Among Students
5. Chegg Products
6. The Feature We Will Talk About
7. The app takes forever to load anything if it loads it at all... Don't like how you don't have the option to use the mobile site they force you into using their slow app.. Sticking with the desktop service... How about put my money to good use and fix your app Here our journey began
9. public Integer isOk(Object obj){ if (obj instanceOf Image){ Image objectAfterCasting = (Image) obj; int a = objectAfterCasting.created; int b = objectAfterCasting.fileSize; int c = objectAfterCasting.width; int d = objectAfterCasting.height; if (a> 968876155 && (b * 1024 >9 || b *1024 < 7) && ((c>300 || d>1000) ||c>d*2)) { objectAfterCasting.status = 2; .... errorHandler(6,obj); // another 60 lines of code!! You’re probably thinking of..
10. Poorly written program, legacy code actually describes a code base that is no longer engineered but continuously patched How does the Community define Legacy code?
11. “Code without unit tests” (Michael Feathers, Working Effectively with Legacy Code) How do the TDD developers define Legacy code?
12. • Hard to maintain, improve, and expand Why is Legacy code challenging? • Difficult to read and follow
13. • Stable • Secure • Feature Rich • High Performance Telegram Paradox • Confusing Names • God Activites • Huge Methods • Magic numbers VS
14. Good Code Structure
15. Let’s explain it
16. New component is added
17. And another one
18. And another one
19. Messy right?
20. How does real Code Object Graphs look like?
21. Can you guess which library this is?
22. And what about this one?
23. Square Libraries
24. • A (false) sense that a small addition to an already complicated logic, won’t make a difference Why do good developers extend messy code? • Broken window theory • More effort to fight existing state
25. • Legacy code is better to be removed and avoided • Good developers write messy code I Hope that you’re convinced that:
26. Back to our journey
27. private void storeSelection() { new Thread() { @Override public void run() { android.os.Process.setThreadPriority (android.os.Process.THREAD_PRIORITY_BACKGROUND); // do some logic storeProblemSelection(); RecentBook recentBook = book.toRecentBook(); runOnUiThread(() -> recentTbsRepo.addBook(recentBook)); } } }.start(); } Legacy code @ Chegg
28. @Override public void handleMessage(Message msg) { switch (msg.what) { case BookDataManager.ON_FAILED_SOLUTION: // Some logic if (msg.obj != null) { error = msg.obj.toString(); if (error.contains("Authenticate")) { // Some Logic } else { showSolutionsNotFoundError(PROBLEM); } } // ~ 15 Different states, Multiple Error states, Complex tangled logic } Legacy code @ Chegg
29. What are our Options?
30. Brute force
31. Rewrite
32. What’s the alternative?
33. “the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure” What is Refactor?
34. • Bug Fixes What is not refactoring • Api Changes • Features
35. • Increase code complexity during the process Why developers don’t refactor code? • Different Problems In code Highly Coupled • Dead lines
36. • Legacy Code == Tech Debt How to Convince The Manager To Refactor? • Debt is usually reasonable only with low interest
37. I’m Ready
38. • Each test can cover a small increment of functionality • Small and ugly changes can be done to make the new tests run • Tests are run very Often • Many teensy-weensy steps make up the refactoring TDD Refactor Approach and Agile Practices
39. Meantime in the Android reality...
40. • Break the fear Approach for refactoring without tests • Small steps • Pick the simple
41. Wait, Refactor messy code to… ? • Robust • Stable • Testable • Modular • Easy to Extend • Simplicity • Readability • Modularity • Layering • Design • Efficiency • Elegance Good Code Is
42. Minimize Refactoring Risk : Tech Design
43. • Small Git commits to the rescue Minimize Refactoring Risk • Code Review: two minds greater than one
44. • Separation of Concerns “Good code is testable code. By that I mean it’s not code that has tests, but it’s at the very least code that you can write tests for.” Mike Nakhimovich What Common For All Android MVx Architectures? • Unit Testable code • Android classes logic free
45. Set-up Architecture Simple rules and advices for systematic refactor
46. • Break to small methods Simple rules and advices for systematic refactor • Delegate • Give meaningful name
47. Back to our journey Stuck in the limbo
48. public interface SolutionsContract { interface View{ void testView(); } interface Presenter{ void test(); } } Step 1: Architecture (MVP)
49. public class SolutionsPresenter implements SolutionsContract.Presenter { private SolutionsContract.View view; @Inject public SolutionsPresenter(SolutionsContract.View view) { this.view = view; } @Override public void test() { view.testView(); } } Step 1 : Add Presenter “Skeleton”
50. protected void loadChapters() { if (mBookDataManager.getChapters() == null) { Logger.d("chapters are NULL, request from server"); mBookDataManager.requestChapters(); return; } Logger.d("Chapters exist"); handleLoadedChapters(); } Find relative small method
51. protected void loadChapters() { if (mBookDataManager.getChapters() == null) { Logger.d("chapters are NULL, request from server"); mBookDataManager.requestChapters(); return; } Logger.d("Chapters exist"); handleLoadedChapters(); } Break and Extract : Small Method
52. private boolean chaptersLoaded(BookDataManager bookDataManager) { if (bookDataManager.getChapters() == null) { Logger.d("chapters are NULL, request from server"); bookDataManager.requestChapters(); return false; } return true; } Break and Extract : Meaningful Name
53. protected void loadChapters() { if (chaptersLoaded(mBookDataManager)) { Logger.d("Chapters exist"); handleLoadedChapters(); } } Break and Extract : Compile
54. public interface SolutionsContract { interface View{ void testView(); } interface Presenter{ void test(); boolean chaptersLoaded(BookDataManager bookDataManager); } } Delegate : First Add the method signature to “Contract”
55. public class SolutionsPresenter implements SolutionsContract.Presenter { .... @Override public boolean chaptersLoaded(BookDataManager bookDataManager) { if (bookDataManager.getChapters() == null) { Logger.d("chapters are NULL, request from server"); bookDataManager.requestChapters(); return false; } return true; } } Delegate : Now the Same code moved to Presenter
56. protected void loadChapters() { if (presenter.chaptersLoaded(mBookDataManager)) { Logger.d("Chapters exist"); handleLoadedChapters(); } } Delegate : Now the Activity Delegate the work to Presenter
57. protected private void loadChapters() { if (presenter.chaptersLoaded(mBookDataManager)) { Logger.d("Chapters exist"); handleLoadedChapters(); } } Take a moment to Small Safe clean up
58. @Override public void onPickerItemSelected(int pickerType, int index) { bookDataManager.indexChanged(pickerType, index, (type) -> { switch (type) { case CheggPicker.CHAPTER: loadChapters(); break; case CheggPicker.PROBLEM: loadProblems(); break; Gain More Simplicity And Readability
59. Fast Forward...
60. Before
61. After
62. You spoke, we listened. In this update: · Load time improvements. So you can access Textbook Solutions sooner. · Bookmarking. Now you can access and manage your bookmarks from the app! Have feedback? We’d love to hear from you. AppFeedback@chegg.com Release What’s New Section
63. The app takes forever to load anything if it loads it at all... Don't like how you don't have the option to use the mobile site they force you into using their slow app.. Sticking with the desktop service... How about put my money to good use and fix your app Fixed loading issues I had previously with the app appreciate the follow up End Of The Journey
64. • Code that usually not touched When not refactor? • Keep the business in mind
65. Legacy Code Evolution
66. Legacy Code Evolution
67. Legacy Code Evolution
68. Legacy Code Evolution
69. Legacy Code Evolution
70. "I am not a great programmer - just a good programmer with great habits." - Kent Beck. Simple Good Code Habits • Code style conventions • Small methods • Good Naming
71. Thank You And Good Luck With Your Journey
72. Questions?