kotlin_skill

Overview

This skill teaches battle-tested Kotlin coding standards focused on null safety, coroutines, and idiomatic patterns for JVM and Android projects. It provides compact reference patterns, implementation guidance, and tooling recommendations to start a project correctly and safely. Use it to enforce consistent, maintainable, and type-safe asynchronous code.

How this skill works

The skill inspects common Kotlin patterns and prescribes safe alternatives: nullable types, smart casts, scope functions, and delegation. It covers coroutine usage (suspend functions, builders, Flow/StateFlow), collection functional idioms, Java interoperability, and testing patterns. It also recommends linters and static-analysis tools to enforce rules across a codebase.

When to use it

• Starting a new JVM or Android project and want consistent Kotlin standards from day one
• Refactoring code to remove null-safety hazards and platform-type assumptions
• Designing async workflows with coroutines, Flow, or StateFlow
• Introducing functional collection transformations and lazy evaluation
• Setting up CI checks with detekt and ktlint for Kotlin code quality

Best practices

• Prefer nullable types and safe calls over the not-null assertion (!!)
• Favor immutable vals; use var only when mutation is required
• Use data classes for DTOs and sealed classes for restricted hierarchies
• Adopt structured concurrency: prefer coroutineScope/withContext over global scopes
• Use scope functions (let/apply/also/run/with) consistently for clarity
• Integrate detekt and ktlint to enforce style and catch issues early

Example use cases

• Implement a repository layer using suspend functions and withContext(Dispatchers.IO)
• Model UI state with sealed classes and expose it via StateFlow for Compose or LiveData
• Build concurrent API calls with async/await inside coroutineScope to aggregate results
• Create custom property delegates for SharedPreferences or observable properties
• Migrate Java interop code by making platform types explicit and adding @JvmStatic/@JvmOverloads where needed