Wallapop as? Lego

Static libraries... Dynamic Frameworks... We may have a guide about how to build our app modules but, in the end, we always end up with something like a Lego monster, don't we? At Wallapop, we work on a large Swift + Objective-C codebase that's been living for 6 years now, with 9 iOS developers, you can imagine the kind of headache this might be. Come and see how we're putting all the blocks together.

Transcript

1. iOS Team wallapop as? Lego
2. iOS Team @bitomule @amartinezmes @machipla
3. iOS Team What is this all about?
4. iOS Team Concepts
5. iOS Team Static library vs dynamic framework
6. iOS Team Links at start time Less app size Static library vs dynamic framework Static Dynamic Links at compile time Bigger app size Slower start time Faster start time Imported needs recompiling No need for recompile
7. iOS Team Wich one do we use then? Objective-C code & Third party libraries
8. iOS Team Initialization time
9. iOS Team Carthage + Pods history
10. iOS Team Another concept…
11. iOS Team What do we understand for a module?
12. iOS Team - It’s a .pbxproj, compiled as static library - It can be horizontal (Divided in layers) - It can be vertical (Divided in features) A module for us is…
13. iOS Team Let’s start with the matter!
14. iOS Team Clue: It’s not for fun… at least in part… Why do we modularize? - Compiler limit error - wallapop becoming a huge target - Many other advantages…
15. iOS Team Approaches 1st approach 2nd approach Horizontal Vertical
16. iOS Team Projects + Carthage + Pods Pods Projects + Pods Which where the steps?
17. iOS Team Cool, but…
18. iOS Team What advantages we found on the way?
19. iOS Team Sample projects Show me the advantages! Improve compilation times Fix CI errors Code encapsulation Make clean interfaces AVOID DEVELOPER NIGHTMARES
20. iOS Team
21. iOS Team * This image may not represent yet the actual status of the wallapop iOS Dev team
22. iOS Team Highway to nightmares
23. iOS Team Classic iOS App (Monolith)
24. iOS Team Classic iOS App modules App Module A Module B Module C Common
25. iOS Team How this usually ends?
26. iOS Team Steps we followed
27. iOS Team Modules dependency Module User Module Item Interface module User Interface module Item
28. iOS Team Our module interface rules No third party libraries Know other modules Lightweight No resources Development pod Protocols No implementation ⛔
29. iOS Team Interface example public protocol ChatInterface { func showInbox() func existsConversation(_ id: String) -> Bool func createConversation(userId: String, itemId: String) }
30. iOS Team Our module project rules CocoaPods Third party ⛔ Other project No resources Workspace project Public implementation Only knows interfaces Test
31. iOS Team Module structure Source code Unit test Snapshot test Example project Other module interfaces Development pods Third party
32. iOS Team
33. iOS Team
34. iOS Team We’ve solved dependency between modules but…
35. iOS Team What if the module needs the APP?
36. iOS Team Legacy interface to the rescue - It’s a development pod - Follows the same module interface rules - Easy to mock
37. iOS Team Modules interfaces Chat Shipping Ads PROs wallapop as! Lego Discovery Storage Realtime API Client Legacy Dependency injection Third party libraries Modules Responsibility Development pods Dependencies Main App
38. iOS Team Dependency injection
39. iOS Team No standard way of doing it
40. iOS Team There’s a popular library - Swinject - More than 3000 stars on GitHub - No code generation required
41. iOS Team We did our own WIP
42. iOS Team How does it work? let dependencyContainer = DependencyContainer() dependencyContainer.register(ItemInterface.self, dependency: Item()) dependencyContainer.resolve(ItemInterface.self).resolve()
43. iOS Team How does it work? let dependencyContainer = DependencyContainer() dependencyContainer.register(ItemInterface.self, dependency: Item()) dependencyContainer.resolve(ItemInterface.self).resolve()
44. iOS Team How does it work? let dependencyContainer = DependencyContainer() dependencyContainer.register(ItemInterface.self, dependency: Item()) dependencyContainer.resolve(ItemInterface.self).resolve()
45. iOS Team Problems
46. iOS Team - Circular dependencies Problems - Optional vs force unwrap
47. iOS Team Item needs User User needs Item Circular dependency
48. iOS Team - Resolve dependency inside a closure How did we solve it? - Force unwrap as a compromise
49. iOS Team let item = Item(user: container.resolve(UserInterface.self)) container.register(ItemInterface.self, item) Resolve dependency inside a closure
50. iOS Team let item = Item(user: container.resolve(UserInterface.self)) container.register(ItemInterface.self, item) Resolve dependency inside a closure
51. iOS Team let user = User(item: container.resolve(ItemInterface.self)) container.register(UserInterface.self, user) Resolve dependency inside a closure
52. iOS Team let user = User(item: container.resolve(ItemInterface.self)) container.register(UserInterface.self, user) Resolve dependency inside a closure
53. iOS Team Module details
54. iOS Team ✅ Public interface ✅ Private implementation - Tests - Example app
55. iOS Team Tests
56. iOS Team - Test module internal implementation - Fast Tests
57. iOS Team Really fast
58. iOS Team - Unit tests - Snapshot tests Each module contains:
59. iOS Team - Quick - Nimble - SnapshotTesting by Pointfree We’re using:
60. iOS Team Example project
61. iOS Team Important advantage of modules
62. iOS Team Enables faster development and prototyping
63. iOS Team Is is not an easy process
64. iOS Team - Dependencies - Repeat base code Is is not an easy process
65. iOS Team How we made it easier
66. iOS Team - Shared base example code - Mocked dependencies How we made it easier
67. iOS Team
68. iOS Team Mocked dependencies
69. iOS Team Mocked dependencies - Generated using Sourcery - Avoids having to mock dependencies manually in each example app - Used for example apps
70. iOS Team Generated using Sourcery - Code generation tool for Swift - Built on top of SourceKit - github.com/krzysztofzablocki/Sourcery
71. iOS Team Q&A wallapop si no lo usas, súbelo
72. iOS Team Where’s the closure?
73. iOS Team init(moduleB: @autoclosure @escaping () -> B)