VIPERtoSwiftUI

GOAL

This app presents few examples for common patterns using purer (from authors experience) SwiftUI code.

LITERATURE

1. https://www.appypie.com/pass-data-between-views-swiftui-how-to
2. https://www.hackingwithswift.com/articles/216/complete-guide-to-navigationview-in-swiftui
3. https://www.raywenderlich.com/8440907-getting-started-with-the-viper-architecture-pattern#toc-anchor-004

(last visited 12/2021)

MVVM vs VIPER

• Viper is used for additional separation of concerns, in most of the most cases not needed in modern mobile app development!
• Mvvm separation should suffice in most of nowadays mobile app screens/features - which are lightweight, modular, recyclable.

Happy to hear arguments against these thoughts/statements - will argue back and change my opinion if yours arguments are stronger/better :)

VIPER

• Router is implementation of principle - inversion of control, knows how to create each View with everything needed for that View to live happily.

• Entity is object containing/wrapping/uniting all variables. Multiple entities enable syntacticall / logic separation of concerns.

• Interactor is point of interaction for various presenters to handle user interaction with app/feature. Multiple interactors enable syntacticall / logical separation of concerns (preceeded by multiple Entity instances).

• Presenter is instance, wrapped in @ObservableObject that triggers UI changes. Multiple presenters enable syntactically / logical separation of concerns (for each View where View is lowest hierarchical UI unit we want to control dinamically in feature).

• View is lowest hierarchical UI unit (e.g. SwiftUI View subview) we want to control dinamically in feature. Multiple views, well, you get that part by now hopefully. Multiple views, all passive UI elements, are grouped in (theirs) parent View which is controlled by respective Presenter instance.

EXAMPLES

2. Navigation flow with passing data forw-backw in setup StartView-MediatorView-FinalView.
   In which data is presented on StartView and changed in FinalView.
   MediatorView and FinalView are dismissed withouth transitions between.
3. Data presented on View is always re-rendered (core paradigm of and goal of usage of SwiftUI) but data is consistent because it comes from @Environment instance.