How to structure your files with VIPER Architecture

Maybe you already had the theory of how VIPER Architecture work but that's only the THEORY, in the real work can be painful implement a Software Architecture because you can have a lot of cases that you can't know how to implement correctly accordly VIPER Architecture (But this can happen when whatever Architecture).

I'll explain you how to implement correctly VIPER with a common cases, but if you have an especific scenario you can comment to discuss how VIPER can solvent correctly.

PhonebookApp (iOS)

A classic one. Let's supouse that you need to do a simple Phonebok application where stores contact.

PhonebookApp # Root directory of the application

├── Common # Shared code between features
│   ├── Models # Data models representing entities
│       ├── Contact.swift # Represents a single contact with its information
│       └── ContactGroup.swift # Represents a group of contacts
│   ├── Utils # Utility classes for common functionalities
│       ├── NetworkManager.swift # Handles communication with network services
│       └── StorageManager.swift # Handles data persistence and retrieval
│   └── ViewModels # View models for data presentation
│       ├── ContactDetailViewModel.swift # Prepares data for the contact detail view
│       ├── ContactGroupListViewModel.swift # Prepares data for the contact group list view
│       └── ContactListViewModel.swift # Prepares data for the contact list view
├── Features # Individual features of the application # Feature for managing a single contact
    ├── ContactDetail
        ├── Views # UI components for displaying the contact
        │   └── ContactDetailView.swift # Xcode Storyboard or SwiftUI view for contact details
        ├── Interactors # Business logic for contact data
        │   └── ContactDetailInteractor.swift # Fetches, updates, and deletes contact data
        ├── Presenters # Prepares data for the contact detail view
        │   └── ContactDetailPresenter.swift # Receives data from interactor and formats it for view
        └── Routers # Navigation logic for the contact detail screen
            └── ContactDetailRouter.swift # Handles navigation to other features from contact detail # Feature for managing contact groups
    ├── ContactGroupList
        ├── Views # UI components for displaying contact groups
        │   └── ContactGroupListView.swift # Xcode Storyboard or SwiftUI view for contact group list
        ├── Interactors # Business logic for contact group data
        │   └── ContactGroupListInteractor.swift # Fetches, updates, and manages contact groups
        ├── Presenters # Prepares data for the contact group list view
        │   └── ContactGroupListPresenter.swift # Receives data from interactor and formats it for view
        └── Routers # Navigation logic for the contact group list screen
            └── ContactGroupListRouter.swift # Handles navigation to other features from contact group list # Feature for managing the list of contacts
    └── ContactList
        ├── Views # UI components for displaying contacts
        │   └── ContactListView.swift # Xcode Storyboard or SwiftUI view for contact list
        ├── Interactors # Business logic for contact data
        │   └── ContactListInteractor.swift # Fetches, updates, and manages contacts
        ├── Presenters # Prepares data for the contact list view
        │   └── ContactListPresenter.swift # Receives data from interactor and formats it for view
        └── Routers # Navigation logic for the contact list screen
            └── ContactListRouter.swift # Handles navigation to other features from contact list
├── App # Entry point and core application logic
│   ├── AppDelegate.swift # Manages the application lifecycle
│   ├── SceneDelegate.swift # Manages window scene lifecycle and transitions on iOS 13+
│   └── MainCoordinator.swift # Coordinates navigation between features
├── Tests # Unit tests for application components
│   ├── CommonTests # Tests for shared code
│       ├── ModelsTests.swift # Unit tests for `Contact` and `ContactGroup` models
│       └── UtilsTests.swift # Unit tests for `NetworkManager` and `StorageManager`
│   ├── FeaturesTests # Tests for individual features
│       ├── ContactDetailTests.swift # Unit tests for contact detail functionality
│       ├── ContactGroupListTests.swift # Unit tests for contact group list functionality
│       └── ContactListTests.swift # Unit tests for contact list functionality
│   └── AppTests # Tests for application entry point
│       └── AppDelegateTests.swift # Unit tests for `AppDelegate`
└── Resources # Assets and configuration files
    ├── Images.xcassets # App icons and other images
    ├── LaunchScreen.storyboard # Storyboard for the launch screen
    └── Info.plist # Configuration file for the application

Shop App (Android)

ShopApp
├── app
│   ├── build.gradle
│   ├── src
│       ├── main
│           ├── AndroidManifest.xml
│           ├── assets
│           │   └── ... # app assets like images
│           ├── java
│               └── com.yourcompany.shop
│                   ├── data
│                       ├── model
│                           ├── Product.java # Represents a product with details
│                           └── ProductCategory.java # Represents a product category
│                   ├── network
│                       └── ApiManager.java # Handles network communication
│                   ├── persistence
│                       └── LocalStorage.java # Handles data persistence on device
│                   ├── repository
│                       └── ProductRepository.java # Provides access to product data
│                   ├── features
│                       ├── productdetail  # Feature for managing a single product detail
│                       │   ├── contract
│                       │   │   ├── ProductDetailContract.kt # Interface for VIPER communication
│                       │   │       ├── ProductDetailView.kt # Interface for View
│                       │   │       ├── ProductDetailInteractor.kt # Interface for Interactor
│                       │   │       ├── ProductDetailPresenter.kt # Interface for Presenter
│                       │   │       └── ProductDetailRouter.kt # Interface for Router
│                       │   ├── data
│                       │   │   └── ProductDetailRepositoryImpl.kt # Implementation of ProductRepository for product detail
│                       │   ├── presentation
│                       │   │   ├── ProductDetailPresenterImpl.kt # Implementation of ProductDetailPresenter
│                       │   ├── ui
│                       │   │   └── ProductDetailActivity.kt # Activity for displaying product details
│                       │   └── ... (other implementation classes)
│                       ├── productlist  # Feature for managing the product list
│                       │   ├── contract
│                       │   │   ├── ProductListContract.kt # Interface for VIPER communication
│                       │   │       ├── ProductListView.kt # Interface for View
│                       │   │       ├── ProductListInteractor.kt # Interface for Interactor
│                       │   │       ├── ProductListPresenter.kt # Interface for Presenter
│                       │   │       └── ProductListRouter.kt # Interface for Router
│                       │   ├── data
│                       │   │   └── ProductListRepositoryImpl.kt # Implementation of ProductRepository for product list
│                       │   ├── presentation
│                       │   │   ├── ProductListPresenterImpl.kt # Implementation of ProductListPresenter
│                       │   ├── ui
│                       │   │   └── ProductListActivity.kt # Activity for displaying product list
│                       │   └── ...
│                   ├── ...
│                   └── util
│                       └── ... # Utility classes
│   └── gradle.properties
│   └── gradlew.bat  # or gradlew (depending on OS)
├── build.gradle
├── gradle.properties
└── local.properties # Optional for local development configuration