Book Image

Hands-On Design Patterns with Kotlin

By : Alexey Soshin
Book Image

Hands-On Design Patterns with Kotlin

By: Alexey Soshin

Overview of this book

Design patterns enable you as a developer to speed up the development process by providing you with proven development paradigms. Reusing design patterns helps prevent complex issues that can cause major problems, improves your code base, promotes code reuse, and makes an architecture more robust. The mission of this book is to ease the adoption of design patterns in Kotlin and provide good practices for programmers. The book begins by showing you the practical aspects of smarter coding in Kotlin, explaining the basic Kotlin syntax and the impact of design patterns. From there, the book provides an in-depth explanation of the classical design patterns of creational, structural, and behavioral families, before heading into functional programming. It then takes you through reactive and concurrent patterns, teaching you about using streams, threads, and coroutines to write better code along the way By the end of the book, you will be able to efficiently address common problems faced while developing applications and be comfortable working on scalable and maintainable projects of any size.
Table of Contents (13 chapters)

Chain of responsibility

I'm a horrible software architect, and I don't like to speak with people. Hence, while sitting in The Ivory Tower (that's the name of the cafe I often visit), I wrote a small web application. If a developer has a question, he shouldn't approach me directly, oh no. He'll need to send me a proper request through this system, and I shall answer him only if I deem this request worthy.

A filter chain is a very common concept in web servers. Usually, when a request reaches to you, it's expected that:

  • Its parameters are already validated
  • The user is already authenticated, if possible
  • User roles and permissions are known, and the user is authorized to perform an action

So, the code I initially wrote looked something like this:

fun handleRequest(r: Request) {
// Validate
if (r.email.isEmpty() || r.question.isEmpty()) {
...