shared-models

Shared Models for KMP

Design and implement data models that work across all platforms in shared/commonMain.

Core Dependencies

// build.gradle.kts (shared module)
sourceSets {
    val commonMain by getting {
        dependencies {
            implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.6.0")
            implementation("org.jetbrains.kotlinx:kotlinx-datetime:1.6.0")
        }
    }
}

Enable serialization plugin:

plugins {
    kotlin("multiplatform")
    kotlin("plugin.serialization") version "1.9.20"
}

Domain Models

1. Immutable Data Classes

// commonMain/kotlin/com/example/shared/model/User.kt
@Serializable
data class User(
    val id: String,
    val name: String,
    val email: String,
    val avatarUrl: String?,
    val createdAt: Instant,
    val lastActiveAt: Instant?
)

2. Sealed Hierarchies

// commonMain/kotlin/com/example/shared/model/UiState.kt
@Serializable
sealed class UiState<out T> {
    @Serializable
    data object Loading : UiState<Nothing>()

    @Serializable
    data class Success<T>(val data: T) : UiState<T>()

    @Serializable
    data class Error(val message: String, val code: String? = null) : UiState<Nothing>()
}

// Usage with type parameter
@Serializable
sealed class HomeState {
    @Serializable
    data object Loading : HomeState()

    @Serializable
    data class Loaded(val user: User, val items: List<Item>) : HomeState()

    @Serializable
    data class Error(val message: String) : HomeState()
}

3. Result Wrapper

// commonMain/kotlin/com/example/shared/model/Result.kt
@Serializable
sealed class Result<out T> {
    @Serializable
    data class Success<T>(val data: T) : Result<T>()

    @Serializable
    data class Error(val code: String, val message: String) : Result<Nothing>()
}

// Helper to convert from Kotlin Result
fun <T> Result<T>.toKotlinResult(): kotlin.Result<T> = when (this) {
    is Result.Success -> kotlin.Result.success(data)
    is Result.Error -> kotlin.Result.failure(RuntimeException("$code: $message"))
}