everything-claude-code-mobile: Skill for Claude Code

expect/actual Pattern for KMP

The expect/actual declaration is Kotlin's mechanism for writing platform-specific implementations while maintaining a shared API surface.

Core Concept

// shared/commonMain/kotlin/Platform.kt
expect class Platform() {
    val name: String
}

// shared/androidMain/kotlin/Platform.android.kt
actual class Platform {
    actual val name: String = "Android ${Build.VERSION.SDK_INT}"
}

// shared/iosMain/kotlin/Platform.ios.kt
actual class Platform {
    actual val name: String = "iOS \(UIDevice.currentDevice.systemVersion)"
}

Common Patterns

1. Platform Information

// commonMain
expect object Platform {
    val name: String
    val version: String
    val isDebug: Boolean
}

// androidMain
actual object Platform {
    actual val name: String = "Android"
    actual val version: String = "${Build.VERSION.SDK_INT}"
    actual val isDebug: Boolean = BuildConfig.DEBUG
}

// iosMain
actual object Platform {
    actual val name: String = "iOS"
    actual val version: String = UIDevice.currentDevice.systemVersion
    actual val isDebug: Boolean = KotlinLifecycleController.isDebug
}

2. File System Paths

// commonMain
expect class FileSystem {
    fun getDocumentsPath(): String
    fun getCachePath(): String
    fun getTempPath(): String
}

// androidMain
actual class FileSystem {
    actual fun getDocumentsPath(): String {
        return context.filesDir.absolutePath
    }
    actual fun getCachePath(): String {
        return context.cacheDir.absolutePath
    }
    actual fun getTempPath(): String {
        return context.cacheDir.absolutePath + "/tmp"
    }
}

// iosMain
actual class FileSystem {
    actual fun getDocumentsPath(): String {
        return NSSearchPathForDirectoriesInDomains(
            NSDocumentDirectory,
            NSUserDomainMask,
            true
        ).first() as String
    }
    actual fun getCachePath(): String {
        return NSSearchPathForDirectoriesInDomains(
            NSCachesDirectory,
            NSUserDomainMask,
            true
        ).first() as String
    }
    actual fun getTempPath(): String {
        return NSTemporaryDirectory()
    }
}