Splitting Monolithic Swift Code Base Into Modules

Modular Architecture - insights from a big French e-commerce. How to challenge the status quo, boost team motivation, productivity and start writing cleaner code with more tests? A journey of sailing from monolithic codebase to modules.

- how do we switch to a MVVM+C architecture within existing Swift code base?
- how do we approach splitting the monolith into modules?
- how do we boost features development with product modules?
- how do we get rid of Core Data?
- is TDD possible in a slowly compiling Swift code base?
- what are some unobvious benefits of code modularization?

Transcript

1. Paul-Emmanuel Garcia iOS Developer, Product team @pemgarcia Maciej Grzybowski iOS Lead Developer, Core team @ncreated
3. up to 1M daily active users release every 2 weeks flash sales peak at 7AM
4. Company organization Product Team Product Team Product Team ... ... Lead Dev UX PO QA iOS, Android, Web, backend DEVS
5. The iOS chapter - 10 iOS Engineers - 7 in Product Teams - 3 in Core Team Product Team Product Team Product Team Product Team ... ... CORE Team
6. Our code base was not in a good shape - hard to understand - long to compile - slow test feedback - little test coverage - difficult to refactor - little reusability
7. Monolith The problem - monolith
8. Pain points - exploding complexity - fat, static objects - massive view controllers - low test coverage complex code devs go quick & dirty
9. Pain points - too little abstraction bad abstraction devs go quick & dirty
10. Pain points - mess photo by Rick Mason - @egnaro at unsplash.com mess devs duplicate, not reuse
11. Pain points - waiting time photo by Pixpoetry - @blackpoetry at unsplash.com frustration no change
12. code base size development friction team happiness
13. Monolith Monolith Framework The cure - modularization Framework Framework Framework
19. UI components Custom fonts Shared utilities
21. VM + VC Coordinator VM + VC VM + VC API Responses Business Models
22. VM + VC Coordinator VM + VC VM + VC API Responses Business Models marketplaceCoordinator.start()
23. VM + VC Coordinator VM + VC VM + VC API Responses Business Models marketplaceCoordinator.start()
25. VM + VC VM + VC VM + VC
26. VM + VC VM + VC VM + VC UserEngagementCoordinator UE API Responses UE Business Models create create create
27. VM + VC VM + VC VM + VC ScreensViewController create create create
28. ?
29. - quick iteration on single screens - quick iteration on entire flow - efficient for legacy code - efficient for new features Coordinator UserEngagementCoordinator
30. class DataManager ... LoginViewController let dataManager: DataManager
31. class DataManager ... LoginViewController let dataManager: DataManager
32. class DataManager ... LoginViewController let dataManager: DataManager protocol DataManagerType
33. class DataManager ... LoginViewController let dataManager: DataManagerType public protocol DataManagerType
34. class DataManager ... LoginRepository public protocol DataManagerType LoginViewModel LoginViewController
35. class DataManager ... LoginRepository LoginViewModel LoginViewController HTTPClient
36. class DataManager ... LoginRepository LoginViewModel LoginViewController HTTPClient
37. LoginRepository LoginViewModel LoginViewController HTTPClient
39. Modules ... ...
40. Dependencies ... ...
41. Dependencies ... ...
42. Monorepository - no versioning problems - quick iterations on modules - single GitLab project
43. GitLab workflow
44. Monolith Framework Framework Framework Framework Monolith
45. New shape of our code base - easier to understand - faster to compile - has better test coverage - gives quicker test feedback - invites for reusability - simpler to refactor - faster features development - happier developers!
46. It was a long term investment for us code base size feature development effort with modules with monolith
47. Paul-Emmanuel Garcia iOS Developer, Product team @pemgarcia Maciej Grzybowski iOS Lead Developer, Core team @ncreated We are hiring! https://l.vpgrp.io/vptechcareers https://careers.vente-privee.com/en/vptech/