Structuring Your Code With MVP

MVC or Model View Controller has been the tried and true way for iOS programmers for years, but nowadays developers find it hard to test, structure and that it violates a few key architecture principles. Enter Model-View-Presenter, a much cleaner architecture that allows for separation of concerns, easier testing, and greater programmer happiness. This talk covers programming a standard iOS use case putting data from the server onto a screen, with the MVP pattern, plus a few other patterns to allow for maintainable and scalable iOS development.

Transcript

1. /dev/world Structuring Your Code With MVP Sam Jarman iOS Developer, Bank of New Zealand 2018 @samjarman
2. /dev/world ’18 • @samjarman Who Am I? • iOS Developer at the Bank of New Zealand • iOS Dev since ages ago • Sabbatical in Ruby on Rails, EmberJS, AWS, more • Twitter friendly talk!
3. /dev/world ’18 • @samjarman Today A story of Evolution
4. /dev/world ’18 • @samjarman Age of Empires Arguably my favourite game
5. /dev/world ’18 • @samjarman Ages in Age of Empires • Dark Age • Tool Age • Bronze Age • Iron Age
6. /dev/world ’18 • @samjarman The Dark Age
7. /dev/world ’18 • @samjarman 2009ish
8. /dev/world ’18 • @samjarman MVC
9. /dev/world ’18 • @samjarman Model View Controller
10. /dev/world ’18 • @samjarman Model Controller View
11. /dev/world ’18 • @samjarman Model Controller View TableView CollectionView Customer Thing Object Control and coordinate
12. /dev/world ’18 • @samjarman Model Controller View TableView CollectionView Customer Thing Object Network Caching Data Access / Persistence Control and coordinate View Datasources View Delegates
13. /dev/world ’18 • @samjarman Model Controller View TableView CollectionView Customer Thing Object Network Caching Data Access / Persistence All the things…. View Datasources View Delegates
14. /dev/world ’18 • @samjarman Controller • Delegate for TableView • Datasource for TableView • Network calls • Parsing of DTOs into models • Sorting of arrays • SQL/CoreData • Sizing cells • … more!
15. /dev/world ’18 • @samjarman Massive View Controller
16. /dev/world ’18 • @samjarman Massive View Controllers are the hidden shame of every iOS Developer
17. /dev/world ’18 • @samjarman The Problem • Controllers doing too much • Almost no well defined inputs and outputs • Tonnes of side effects • No real consequences of this programmer behaviour
18. /dev/world ’18 • @samjarman Then: The gold rush was over Stop mixing metaphors, Sam Shushhh
19. /dev/world ’18 • @samjarman We Wanted…
20. /dev/world ’18 • @samjarman We Wanted… Products not experiments Longevity Apps as a strategy Readability Teams of developers Maintainability To use source control To release with confidence To keep up with OS updates To make good apps
21. /dev/world ’18 • @samjarman It’s time to advance to the next age
22. /dev/world ’18 • @samjarman The Tool Age
23. /dev/world ’18 • @samjarman Desirable Code What does good code look like?
24. /dev/world ’18 • @samjarman Desirable Code • Single responsibility • Clear inputs and outputs • SOLID • Unit Testable • (… and a lot more!)
25. /dev/world ’18 • @samjarman The Solution • Thoughtfully architect your app
26. /dev/world ’18 • @samjarman Clean, maintainable code comes from thoughtful app architecture
27. /dev/world ’18 • @samjarman Good architecture is the act of decomposing your apps functionality into single responsibility objects with clear inputs and outputs
28. /dev/world ’18 • @samjarman Possible Solutions • There are plenty of possible solutions and architectures for your app • MVP, MVVM, VIPER, More… • Lets chat about one today! Tuesday, 2:00 PM VIPER for iOS Thomas Verbeek
29. /dev/world ’18 • @samjarman MVP Model View Presenter
30. /dev/world ’18 • @samjarman MVP Model View Presenter ^Controller + Provider + View
31. /dev/world ’18 • @samjarman Presenter Provider ViewController View Model Network/Disk
32. /dev/world ’18 • @samjarman View • A standard iOS View • Could contain a tableview, collection view, stack views, whatever your heart* desires *pragmatic implementation of designs
33. /dev/world ’18 • @samjarman View (Controller) • A view controller • Acts as delegate / datasource of TV/CV etc • Layout and populates views • Receives user actions • Asks and informs the presenter
34. /dev/world ’18 • @samjarman Presenter • Interacts with Data provider classes • Instructs view what to do • Doesn’t know/care about the view
35. /dev/world ’18 • @samjarman Provider • Reads/Writes to the source of truth • Server • Database • Other • Constructs models from that source • Passes models back to presenter
36. /dev/world ’18 • @samjarman Model • A class or struct with properties • Represents an object • Maybe created by server response directly or Domain Transfer Object • Maybe failable init?
37. /dev/world ’18 • @samjarman Presenter Provider ViewController View Model Network/Disk
38. /dev/world ’18 • @samjarman Communication How does it work in MVP?
39. /dev/world ’18 • @samjarman Presenter Provider ViewController View Model Network/Disk Delegate UIKits standard Method Call Delegate Method Call
40. /dev/world ’18 • @samjarman Ownership
41. /dev/world ’18 • @samjarman Presenter Provider ViewController View Model Network/Disk Weak delegate Owns (Strong*) Owns(Strong) Weak delegate Owns (Strong) Constructs Owns/Singleton
42. /dev/world ’18 • @samjarman Code Walkthrough
43. /dev/world ’18 • @samjarman Unit testing
44. /dev/world ’18 • @samjarman Presenter Provider ViewController View Model Network/Disk Delegate UIKits standard Method Call Delegate Method Call
45. /dev/world ’18 • @samjarman Unit testing • Clear inputs ✅ - Interface • Clear outputs ✅ - Delegate/Protocol • Clear side affects ✅ - Only in provider! • Single responsibility ✅
46. /dev/world ’18 • @samjarman –Me, excited about unit testing decent architecture “We can unit test the crap out of this thing”
47. /dev/world ’18 • @samjarman Anatomy of a test • Setup / Given • Run / When • Verify / Then
48. /dev/world ’18 • @samjarman Anatomy of a test Presenter Mock Delegate + Recording Method Call
49. /dev/world ’18 • @samjarman Demo of Tests
50. /dev/world ’18 • @samjarman A word on tests
51. /dev/world ’18 • @samjarman If you’re finding your tests hard to write, revise your code.
52. /dev/world ’18 • @samjarman And that’s MVP • Logical units of work • Clear inputs, clear outputs, no side effects • Possible to 100% unit test non-UI • Use of interfaces and delegates for communication
53. /dev/world ’18 • @samjarman MVP is… • An option for you to structure your code • A light weight architecture for those new to architecting code
54. /dev/world ’18 • @samjarman MVP is not.. • The only way to do this • A solution for all use cases, teams, and code bases • An end to all bugs • Noticeable to your users… for now
55. /dev/world ’18 • @samjarman What’s next?
56. /dev/world ’18 • @samjarman iosarchitecture.top
57. /dev/world ’18 • @samjarman The Bronze Age
58. /dev/world ’18 • @samjarman The Bronze Age Tuesday, 2:00 PM VIPER for iOS Thomas Verbeek
59. /dev/world ’18 • @samjarman So what’s this all really about?
60. /dev/world ’18 • @samjarman Architectural patterns are about expressing yourself in logical units that are individually replaceable, expandable, testable and interoperable
61. /dev/world ’18 • @samjarman Better patterns: …better code …better apps …better user experience …better for business
62. /dev/world ’18 • @samjarman Thank you!
63. /dev/world ’18 • @samjarman Thank you! • Me? www.samjarman.co.nz • Learn more about SOLID? https:// en.wikipedia.org/wiki/SOLID