[SwiftAveiro] - MVVM World Tour 2016 by Rui Peres

In this talk Rui Peres (@peres) will discuss the Why and the How in MVVM. Finally why things brake independently of the Architecture chosen and what we can do differently to improve our apps

Transcript

2. !
3. MVVM WORLD TOUR 2016
4. WHO IS USING MVVM? ✋
5. AGENDA 1. What is MVVM? ! 2. What do you get with MVVM (versus MVC)? ☺ 3. FAQ # 4. Conclusion ✨
6. 1. WHAT IS MVVM? !
7. MVVM IS AN ARCHITECTURAL PATTERN
12. WHAT DOES UPDATES MEANS? !
13. DELEGATION?
14. !"
15. MVVM + DELEGATION == GLORIFIED MVC
16. 1. Notifications ! 2. KVO " 3. Anonymous Functions #
17. WHAT DOES MICROSOFT, THINKS ABOUT THIS?
18. BINDER !
19. Declarative data- and command- binding are implicit in the MVVM pattern.1 1 https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93viewmodel
20. When implemented outside of the Microsoft stack the presence of a declarative databinding technology is a key enabler of the pattern.2 2 https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93viewmodel
21. WHAT DO YOU GET WITH MVVM (VERSUS MVC)? ☺
22. COMPONENTS ARE NORMALLY MORE REUSABLE, SINCE THEY ARE DECOUPLED FROM WHO OWNS THEM !
23. TESTING BECOMES EASIER !
24. TENDS TO HAVE A BETTER SEPARATION BETWEEN LAYERS ✨
26. BUT...
27. MVVM without a FRP inspired framework is only a small improvement over MVC: it still suffers from the same problem. — Me, just now
28. It doesn't help dealing with flow complexity and state management at a fundamental level. — Me, again
29. 2. FAQ !
30. "I have been hearing a lot about MVVM with Views and ViewModels, but where's the UIViewController now? What's its role?" — Maria João Pires
31. THIS MIGHT SHOCK YOU, BUT... !
32. The UIViewController's role is the same as it was in MVC... !
33. ▸ Part of the View layer ▸ No Business Logic ▸ No Model layer Logic ▸ Normally not reusable
34. "With MVVM in mind, how would you deal with cells?" — Fernando Pessoa
35. EACH HAS ITS OWN VIEWMODEL !
36. UITableViewDataSource func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let viewModel = ... let cell = ... cell.viewModel = viewModel return cell }
37. Cell var viewModel: CellViewModelRepresentable? { didSet { // } }
38. protocol CellViewModelRepresentable { var title: String { get } var description: String { get } func fetchImage(callback: UIImage -> Void) func fetchUpvotes(callback: Int -> Void) }
39. didSet { titleLabel.text = viewModel.title descriptionLabel.text= viewModel.description viewModel.fetchImage {[weak self] image in self?.imageView.image = image } viewModel.fetchUpvotes {[weak self] upvotes in self?.upvotes.text = String(upvotes) } }
40. "I have seen ViewModels with localized strings, sometimes with Colors, other times interacting with the Model layer. What's really the role of the ViewModel? Is it supose to do all this?" — Guilhermina Suggia
41. (...) the view model is responsible for exposing (converting) the data objects from the model in such a way objects are easily managed and consumed. 3 3 https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93viewmodel
42. IT'S PERFECTLY VALID TO PASS A DUMMY VIEWMODEL WITH COLORS AND LOCALIZED STRINGS.
43. ITS THE VIEWMODEL JOB TO PROVIDE THE VIEW THE DATA IT NEEDS
44. "All the examples I have seen, revolve around the ViewModel interactions with the Model layer, does the ViewModel have anything to say about UI flows?" — Carlos Paião
45. I DON'T HAVE A GOOD ANSWER FOR THIS...
46. IDEALLY THE VIEW WOULD HAVE SOMETHING TO MANAGE THIS... !
48. "Does it make sense for one View to have more than one ViewModel? What about the opposite? One ViewModel serving more than one View?" — Luísa Todi
49. ✅
50. ⚠
51. Will I finally get ride of my Massive ViewController with MVVM? — Sequeira Costa
52. MASSIVE VIEWMODEL? !
53. !
54. "Where does MVVM sucks? " — Eça de Queirós
55. COMPLEX UI'S WITH MANY LEVELS !
56. POTENTIAL SOLUTION?
57. VIPER? !
58. FLUX/REDUX !
59. 4. TO CONCLUDE... ✨
60. MVVM IS NOT A RADICAL CHANGE FROM WHAT WE ARE USED TO
61. MVVM IS NOT A SILVER BULLET AND YOU SHOULDN'T BLINDLY FOLLOW THE CURRENT CARGO CULT AROUND IT
62. WHAT MAKES MVVM AWESOME IS ITS SYNERGY WITH FRP FRAMEWORKS ✨
63. FINALLY...
64. ARCHITECTURAL PATTERNS COME AND GO, BUT GOOD ENGINEERING PRINCIPLES STAY 4 4 SOLID principles
65. Q&A ! Rui Peres (@peres)