Practical Design Patterns in Kotlin

Introduction

The book «Hands-on Design Patterns with Kotlin» (2018) by Alexey Soshin is a practical guide that seamlessly combines classic design patterns (GoF) with the modern capabilities of the Kotlin language. Unlike many books that simply list patterns, this work shows how Kotlin's unique features (higher-order functions, sealed classes, delegation, coroutines) allow you to implement the same ideas more concisely, safely, and expressively. The book is aimed at developers already familiar with the basics of Kotlin and aims to elevate their level to confident mastery of architectural techniques.

What the book is about

The book consists of 12 chapters, each dedicated to a group of patterns or a specific area of application. The author begins with an overview of the language and its differences from Java, then sequentially examines creational, structural, and behavioral patterns. Special attention is paid to functional approaches (lambdas, composition, monads) and the idiomatic use of Kotlin to solve typical problems. The book concludes with patterns for concurrent programming (coroutines, channels) and asynchronous systems.

Who this book is for

• Kotlin developers (Android, backend, multiplatform) looking to systematize their knowledge of architecture.
• Java programmers transitioning to Kotlin and seeking examples of "correct" language usage.
• Students and mentors studying design patterns in the context of the modern JVM stack.
• Library and framework authors striving to write concise and extensible code.

What the reader will learn

• How to implement Singleton, Factory, Builder, Prototype in Kotlin without boilerplate code.
• Applying delegation (by lazy, Delegates.observable) to implement Adapter, Decorator, Proxy.
• Using sealed classes and when expressions for the State and Visitor patterns.
• Functional analogs of Strategy, Command, Observer via lambdas and streams.
• Patterns for coroutines: Producer-Consumer, Fan-Out, Actor.
• How to avoid antipatterns and write idiomatic Kotlin code.

Strengths

Practical focus. Each pattern is accompanied by a complete code listing that can be run immediately. The author does not just retell GoF, but shows how Kotlin changes the implementation: for example, companion objects for factories, inline functions for decorators, coroutines for asynchronous chains.

Modernity. The book was published in 2018, but the material remains relevant: Kotlin 1.3+ already contained all the described features. The author even touches on advanced topics such as contravariance and covariance in the context of patterns.

Structure. The logic of presentation goes from simple to complex: from basic patterns to composite and asynchronous ones. Each chapter ends with a summary and self-test questions.

Style. The book is written in a lively, understandable language, without excessive academicism. Examples are accompanied by explanations of why a particular approach was chosen.

Who it is recommended for

The book will be useful to anyone who wants to deepen their understanding of Kotlin and learn to build flexible, maintainable systems. It is ideal for intermediate developers who already write in Kotlin but feel their code could be cleaner and more expressive. Beginners should first master the basic syntax of Kotlin (for example, from the official documentation) and then take on this book. Experienced Java architects will find many interesting techniques that cannot be implemented in Java without third-party libraries.

Overall, «Hands-on Design Patterns with Kotlin» is not just a reference book, but a practical guide that will help the reader move from "code that works" to "code that is easy to read, test, and extend." We recommend it for study to everyone who is serious