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

Fan Out

The goal of the Fan Out design pattern is to distribute work between multiple concurrent processors, also known as workers. To understand it better, let's look again at the previous section but consider the following problem:

What if the amount of work at the different steps in our pipeline is very different?

For example, it takes a lot more time to fetch the HTML content than to parse it. In such a case, we may want to distribute that heavy work between multiple coroutines. In the previous example, only a single coroutine was reading from each channel. But multiple coroutines can consume from a single channel too, thus dividing the work.

To simplify the problem we're about to discuss, let's have only one coroutine producing some results:

fun CoroutineScope.generateWork() = produce {
    for (i in 1..10_000) {
        send("page$i")
    }
   &...