Book Image

Kotlin Design Patterns and Best Practices - Second Edition

By : Alexey Soshin
Book Image

Kotlin Design Patterns and Best Practices - Second Edition

By: Alexey Soshin

Overview of this book

This book shows you how easy it can be to implement traditional design patterns in the modern multi-paradigm Kotlin programming language, and takes you through the new patterns and paradigms that have emerged. This second edition is updated to cover the changes introduced from Kotlin 1.2 up to 1.5 and focuses more on the idiomatic usage of coroutines, which have become a stable language feature. You'll begin by learning about the practical aspects of smarter coding in Kotlin, as well as understanding basic Kotlin syntax and the impact of design patterns on your code. The book also provides an in-depth explanation of the classical design patterns, such as Creational, Structural, and Behavioral families, before moving on to functional programming. You'll go through reactive and concurrent patterns, and finally, get to grips with coroutines and structured concurrency to write performant, extensible, and maintainable code. By the end of this Kotlin book, you'll have explored the latest trends in architecture and design patterns for microservices. You’ll also understand the tradeoffs when choosing between different architectures and make informed decisions.
Table of Contents (17 chapters)
1
Section 1: Classical Patterns
6
Section 2: Reactive and Concurrent Patterns
11
Section 3: Practical Application of Design Patterns

Understanding Event Loop

The goal of the Event Loop design pattern is to continuously check for new events in a queue, and each time a new event comes in, to quickly dispatch it to someone who knows how to handle it. This way, a single thread or a very limited number of threads can handle a huge number of events.

In the case of web frameworks such as Vert.x, events may be requests to our server.

To understand the concept of the Event Loop better, let's go back to our server code and attempt to implement an endpoint for deleting a cat:

val db = Db.connect(vertx)
router.delete("/:id").handler { ctx ->
    val id = ctx.request().getParam("id").toInt()
    db.preparedQuery("DELETE FROM cats WHERE ID = $1")        .execute(Tuple.of(id)).await()
    ctx.end()
}

This code is very similar to what we've written in our tests in the previous...