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
   

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8. MVP/MVC/MVVM is NOT an
   Architecture!
   It’s only responsible for the presentation layer delivery mechanism
   

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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
   

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11. Clean Architecture
    ● Independent of Frameworks
    ● Testable
    ● Independent of Database
    ● Independent of any external agency
    ● Independent of UI
    

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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
    

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16. Main parts of VIPER
    ● View
    ● Interactor
    ● Presenter
    ● Entity
    ● Router
    

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18. View
    Displays what it is told to by the Presenter and relays user input back
    to the Presenter
    

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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
    

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20. Example of View
    

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22. Example of View
    

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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)
    

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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
    

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25. с
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    Example of Presenter
    

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26. Interactor
    Contains the business logic as specified by a use case
    

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27. Interactor
    ● Represents use cases
    ● Regular Java object
    ● No Android framework dependency
    ● Encapsulates application specific business rules
    

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28. с
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    Example of Interactor
    

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29. Entity
    Contains basic model objects used by the Interactor
    

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30. Entity
    ● POJOs
    ● Encapsulates different types of data
    ● Model objects manipulated by an Interactor
    

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31. Example of Entity
    

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32. Router
    Contains navigation logic for describing which screens are shown in
    which order
    

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35. Router
    ● Responsible for passing data between screens
    ● Receives input commands from the Presenter
    ● Responsible for the navigation logic between modules
    

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36. Example of Router
    

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37. Example of Router
    

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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
    

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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
    

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40. Testing
    ● Presentation layer
    ○ Espresso, Robolectric
    ● Domain layer
    ○ JUnit, TestNG, Mockito, PowerMock
    ● Data layer
    ○ Robolectric, JUnit, TestNG, Mockito, PowerMock
    

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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/
    

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42. Thank you!
    Questions?
    Dmytro Zaitsev
    @DmitriyZaitsev
    

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