Top Coins — Kotlin Multiplatform (KMM)

Top Coins is a cross-platform (Android & iOS) crypto analytics app, refactored to KMM from an original Android-only architecture (switch to Android-only).

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Preview

Android	iOS
android.mp4	iOS.mp4

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Modularization Structure (KMM)

app/                        # Android app entry point
iosApp/                     # iOS app (native SwiftUI)
  └── coinlist/             # Coin list feature (ui/, vm/)
  └── priceliveupdate/      # Price live update feature (ui/, vm/)
  └── composeui/            # Compose Multiplatform hosting
  └── ui.common/            # Shared SwiftUI components
  └── util/                 # iOS utilities (Bundle, SharedViewModelStoreOwner)
  └── resources/            # Localization (en.lproj)
shared/                     # KMM umbrella module (exports cross-platform code)
common/
  └── core/                 # Core types, utilities, extensions
  └── data/                 # Repositories, Ktor networking, WebSocket
  └── domain/               # Use cases, domain models
  └── ui/                   # Compose Multiplatform UI theme/components
  └── navigation/           # Cross-platform navigation (JetBrains/AndroidX)
feature/
  └── coinlist/             # Coin list feature module
  └── priceupdate/          # Live price update feature module
build-logic/
  └── convention/           # Custom Gradle convention plugins
  └── security/             # API key encryption plugin

• The shared umbrella module exports all KMM modules for iOS consumption.
• Platform launchers (app, iosApp) host the shared code with platform-specific UI.
• iosApp contains native SwiftUI views that consume shared ViewModels via SKIE bridge.

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KMM Architecture & Principles

• MVVM with multiplatform ViewModel (StateFlow)
• Clean Architecture: distinct domain, data, UI modules
• DI: Koin multiplatform
• Modular: Feature modules, core/domain/data split
• Tests: Unit tests in all major modules (TODO:// Test are mostly android test, KMM commonTest will be added soon)

iOS UI Consumption Strategies:

This project demonstrates two approaches for consuming KMM shared code on iOS:

Strategy	Shared Layer	iOS UI	Example
Compose UI	End-to-end (Data → Domain → ViewModel → UI)	Compose Multiplatform hosted in SwiftUI	Feature screens
ViewModel Consumption	Up to ViewModel (Data → Domain → ViewModel)	Native SwiftUI	CoinList, PriceLiveUpdate

Key Integration Details:

• SKIE Bridge: When using native SwiftUI, SKIE provides seamless Kotlin-to-Swift interoperability (Flows as AsyncSequence, sealed classes as Swift enums, etc.)
• Cross-platform Navigation: JetBrains/AndroidX Compose Navigation ensures navigation logic remains consistent across platforms
• Shared ViewState: ViewModels expose the same UiState sealed classes to both Android Compose and iOS SwiftUI, ensuring consistent behavior

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Clean Code Practices

Principle	How It's Done
Separation of Concerns	Layered Clean Architecture, per-domain modules
Testability	Unit & UI Tests, DI with Koin
Modularity	Feature & domain modules, Compose resource encapsulation
Build Hygiene	Custom Gradle convention plugins
KMM Best-Practices	Platform-specific logic in respective sourceSets, umbrella sharing

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API Key Setup

This app requires API keys from CoinCap and Twelve Data.

1. Register at CoinCap API portal and Twelve Data to get your API tokens.

2. Open (or create) secret/key.properties in your project (the file is ignored by git).

3. Add your keys in the following format:

   KEY_COIN_AUTH=<your CoinCap API token here>
   KEY_12DATA=<your Twelve Data API token here>

4. Never commit this file. It is already gitignored for safety!

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Keystore Configuration

The app requires signing configurations for both debug and release builds.

Debug Build:

• Debug keystore is included: keystore/debug.keystore.jks
• No additional configuration needed

Release Build:

1. Release keystore is included: keystore/release.keystore.jks
2. Obtain the release signing credentials from the developer
3. Add credentials to your global gradle.properties (~/.gradle/gradle.properties):

   COIN_RELEASE_KEY_ALIAS=your_key_alias
   COIN_RELEASE_KEY_PASSWORD=your_key_password
   COIN_RELEASE_STORE_PASSWORD=your_store_password

Build the Project

Android:

# Debug build
./gradlew :app:assembleDebug

# Release build
./gradlew :app:assembleRelease

iOS:

Open iosApp/iosApp.xcodeproj in Xcode and build/run from there, or use the command line:

# Build iOS app (Debug)
xcodebuild -project iosApp/iosApp.xcodeproj -scheme iosApp -configuration Debug -sdk iphonesimulator build

Switch to Android-only

This is the KMM multiplatform branch. For the pure Android app, checkout here.