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

Higher-order functions on collections

We briefly touched on this topic in Chapter 1, Getting Started with Kotlin, but before we can discuss streams, let's make sure that those of us who come from languages that don't have higher-order functions on collections know what they are, what they do, and what the benefits of using them are.

We won't be able to cover all of the functions available on collections, but we'll cover the most widely used ones.

Mapping elements

The map() function takes each element of a collection and returns a new element of a possibly different type. To understand this idea better, let's say we have a list of letters and we would like to output their ASCII values.

First, let's implement it in an imperative way:

val letters = 'a'..'z'
val ascii = mutableListOf<Int>()
for (l in letters) {
    ascii.add(l.toInt())
}

Notice that even for such a trivial task, we had to write...