VIPER: Sexy Architecting or MVP on Steroids

This talk was presented at TechTalks@Lohika - Android, Kyiv, UA
* How to build scalable, flexible and robust system;
* Why MVC/MVP/MVVM is not an architecture;
* What is Clean Architecture;
* Considering VIPER architecture as an adaptation of Bob Martin's CA for mobile projects: main components, principles, pros & cons;
* Explanation of many buzzwords: SRP, Flow of Control, Business Rules, Massive View Controllers etc.

Transcript

1. Sexy Architecting VIPER: MVP on steroids Dmytro Zaitsev Mobile Team Lead
8. MVP/MVC/MVVM is NOT an Architecture! It’s only responsible for the presentation layer delivery mechanism
9. Real-world Android app • Hard to understand • Hard to maintain • The business logic is mixed in Activity/Fragment • High coupled components • MVC -> Massive View Controllers • Hard and often impossible to test
11. Clean Architecture • Independent of Frameworks • Testable • Independent of Database • Independent of any external agency • Independent of UI
15. What is VIPER? • A way of architecting applications which takes heavy inspiration from the Clean Architecture • Divides an app’s logical structure into distinct layers of responsibility • Makes it easier to isolate dependencies • Makes it easier test the interactions at the boundaries between layers • Eliminates Massive View Controllers
16. Main parts of VIPER • View • Interactor • Presenter • Entity • Router
18. View Displays what it is told to by the Presenter and relays user input back to the Presenter
19. View • Is passive • Waits for the Presenter to give it content to display • Never asks the Presenter for data • Determines how the content is displayed • Handles user interaction and input • Simply delegates user’s actions to the Presenter • Awaits for a response telling it what should be displayed next
20. Example of View
22. Example of View
23. Presenter Contains view logic for preparing content for display (as received from the Interactor) and for reacting to user inputs (by requesting new data from the Interactor)
24. Presenter • Knows about the content it maintains and when it should be displayed • Receives input events coming from the View • Applies view logic over this data to prepare the content • Tells the View what to display • Sends requests to an Interactor • Works like a bridge between the main parts of a VIPER module • Receives the data structures coming from the Interactor • Knows when to navigate to another screen, and which screen to navigate to
25. с с Example of Presenter
26. Interactor Contains the business logic as specified by a use case
27. Interactor • Represents use cases • Regular Java object • No Android framework dependency • Encapsulates application specific business rules
28. с с Example of Interactor
29. Entity Contains basic model objects used by the Interactor
30. Entity • POJOs • Encapsulates different types of data • Model objects manipulated by an Interactor
31. Example of Entity
32. Router Contains navigation logic for describing which screens are shown in which order
35. Router • Responsible for passing data between screens • Receives input commands from the Presenter • Responsible for the navigation logic between modules
36. Example of Router
37. Example of Router
38. Why should you use VIPER? • It’s easier to track issues via crash reports • The source code will be cleaner, more compact and reusable • Adding new features is easier • There are less conflicts with the rest of the development team • It’s easier to write automated tests
39. When should you NOT use VIPER? • It’s an overkill for small projects • Causes an overhead when starting new projects • MVP/MVC/MVVM-VIPER mix can cause headaches • Lots of code all over the project
40. Testing • Presentation layer ◦ Espresso, Robolectric • Domain layer ◦ JUnit, TestNG, Mockito, PowerMock • Data layer ◦ Robolectric, JUnit, TestNG, Mockito, PowerMock
41. References • http://mutualmobile.github.io/blog/2013/12/04/viper-introduction/ • http://www.mttnow.com/blog/architecting-mobile-apps-with-bviper-modules • http://fernandocejas.com/2014/09/03/architecting-android-the-clean-way/ • http://fernandocejas.com/2015/07/18/architecting-android-the-evolution/ • https://www.objc.io/issues/13-architecture/viper/ • https://github.com/RxViper/RxViper • https://www.ckl.io/blog/ios-project-architecture-using-viper/ • http://luboganev.github.io/post/clean-architecture-pt2/
42. Thank you! Questions? Dmytro Zaitsev @DmitriyZaitsev