kotlin-patterns

# Kotlin Development Patterns Idiomatic Kotlin patterns and best practices for building robust, efficient, and maintainable applications. ## When to Use - Writing new Kotlin code - Reviewing Kotlin code - Refactoring existing Kotlin code - Designing Kotlin modules or libraries - Configuring Gradle Kotlin DSL builds ## How It Works This skill enforces idiomatic Kotlin conventions across seven key areas: null safety using the type system and safe-call operators, immutability via `val` and `copy()` on data classes, sealed classes and interfaces for exhaustive type hierarchies, structured concurrency with coroutines and `Flow`, extension functions for adding behaviour without inheritance, type-safe DSL builders using `@DslMarker` and lambda receivers, and Gradle Kotlin DSL for build configuration. ## Examples **Null safety with Elvis operator:** ```kotlin fun getUserEmail(userId: String): String { val user = userRepository.findById(userId) return user?.email ?: "unknown@example.com" } ``` **Sealed class for exhaustive results:** ```kotlin sealed class Result<out T> { data class Success<T>(val data: T) : Result<T>() data class Failure(val error: AppError) : Result<Nothing>() data object Loading : Result<Nothing>() } ``` **Structured concurrency with async/await:** ```kotlin suspend fun fetchUserWithPosts(userId: String): UserProfile = coroutineScope { val user = async { userService.getUser(userId) } val posts = async { postService.g...