D-KMP architecture - official sample

This is the official sample of the D-KMP architecture, presenting a simple master/detail app, for Android, iOS and Desktop.
(the Web version will be added at a later stage, when "Compose for Web" and "Kotlin/Wasm" become more mature)

Key features of the D-KMP architecture:

• it uses the latest declarative UI toolkits: Compose for Android and SwiftUI for iOS
• it fully shares the ViewModel (including navigation logic and data layer) via Kotlin MultiPlatform
• coroutine scopes are cancelled/reinitialized automatically, based on the current active screens and the app lifecycle (using LifecycleObserver on Android and the SwiftUI lifecycle on iOS)
• it implements the MVI pattern and the unidirectional data flow
• it implements the CQRS pattern, by providing Command functions (via Events and Navigation) and Query functions (via StateProviders)
• it uses Kotlin's StateFlow to trigger UI layer recompositions
• the navigation state is processed in the shared code, and then exposed to the UI layer:
  • on SwiftUI it seamlessly integrates with the new iOS 16 navigation patterns (NavigationStack and/or NavigationSplitView)
  • on Compose it's a "remembered" data class which works on any platform (unlike Jetpack Navigation, which only works on Android)

you can find more info on these articles:

• D-KMP sample now leverages iOS 16 navigation (february 2023)
• The future of apps: Declarative UIs with Kotlin MultiPlatform (D-KMP) (november 2020)

Data sources used by this sample:

• webservices (using Ktor Http Client)
• local db (using SqlDelight)
• local settings (using MultiplaformSettings)

these are other data sources, not used by this sample, for which popular KMP libraries exist:

• realtime db (using Firestore)
• graphQL (using Apollo GraphQL)
• device bluetooth (using Kable)
• etc...

Instructions to write your own D-KMP app:

If you want to create your own app using the D-KMP Architecture, here are the instructions you need:

SHARED CODE:

View Model

• 🛠️ in the viewmodel/screens folder: create a folder for each screen of the app, containing these 3 files (as shown in the sample app structure above):
  • screenEvents.kt, where the event functions for that screen are defined
  • screenInit.kt, where the initialization settings for that screen are defined
  • screenState.kt, where the data class of the state for that screen is defined
• 🛠️ in the NavigationSettings.kt file in the screens folder, you should define your level 1 navigation and other settings
• 🛠️ in the ScreenEnum.kt file in the screens folder, you should define the enum with all screens in your app
• ✅ the ScreenInitSettings.kt file in the screens folder doesn't need to be modified
• ✅ the 6 files in the viewmodel folder (DKMPViewModel.kt, Events.kt, Navigation.kt, ScreenIdentifier.kt, StateManager.kt, StateProviders.kt) don't need to be modified
• ✅ also DKMPViewModelForAndroid.kt in androidMain and DKMPViewModelForIos.kt in iosMain don't need to be modified

Data Layer

• 🛠️ in the datalayer/functions folder: create a file for each repository function to be called by the ViewModel's StateReducers
• 🛠️ in the datalayer/objects folder: create a file for each data class used by the repository functions
• 🛠️ in the datalayer/sources folder: create a folder for each datasource, where the datasource-specific functions (called by the repository functions) are defined
• ✅ the datalayer/Repository.kt file should be modified only in case you want to add an extra datasource

PLATFORM-SPECIFIC CODE:

Android

• ✅ the App.kt file doesn't need to be modified
• ✅ the MainActivity.kt file doesn't need to be modified
• The composables are used by both Android and Desktop apps:
  • 🛠️ the Level1BottomBar.kt and Level1NavigationRail.kt files in the navigation/bars folder should be modified to custom the Navigation bars items
  • ✅ the TopBar.kt file in the navigation/bars folder doesn't need to be modified
  • ✅ the OnePane.kt and TwoPane.kt files in the navigation/templates folder don't need to be modified
  • ✅ the HandleBackButton.kt file in the navigation folder doesn't need to be modified
  • ✅ the Router.kt file in the navigation folder doesn't need to be modified
  • 🛠️ in the ScreenPicker.kt file in the navigation folder, you should define the screen composables in your app
  • 🛠️ in the screens folder: create a folder for each screen of the app, containing all composables for that screen
  • ✅ the MainComposable.kt file doesn't need to be modified

iOS

• 🛠️ the Level1BottomBar.swift and Level1NavigationRail.swift files in the composables/navigation/bars folder should be modified to custom the Navigation bars items
• ✅ the TopBar.swift file in the composables/navigation/bars folder doesn't need to be modified
• ✅ the OnePane.swift and TwoPane.swift files in the composables/navigation/templates folder don't need to be modified
• ✅ the Router.swift file in the composables/navigation folder doesn't need to be modified
• 🛠️ in the ScreenPicker.swift file in the views/navigation folder, you should define the screen composables in your app
• 🛠️ in the views/screens folder: create a folder for each screen of the app, containing all SwiftUI views for that screen
• ✅ the App.swift file doesn't need to be modified
• ✅ the AppObservableObject.swift file doesn't need to be modified

Desktop

• ✅ the main.kt file doesn't need to be modified
• The composables are used by both Android and Desktop apps:
  • look at the description on the Android section above

Web (not yet implemented)

• The best technology to implement a Web App in Kotlin will be Compose for Web backed by Kotlin/Wasm. However Kotlin/Wasm is still at a very early stage: the first version was just released in February 2023, with Kotlin 1.8.20.
• Compose For Web and Kotlin/Wasm will allow us to build Compose projects seamlessly for the Web, using the same composables we are already using for the Desktop and Android.