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

Builder

Sometimes, our objects are very simple and have only one constructor, be it an empty or non-empty one. But sometimes, their creation is very complex and based on a lot of parameters. We've seen one pattern already that provides a better constructor – the Static Factory Method design pattern. Now, we'll discuss the Builder design pattern, which will help us create complex objects.

As an example of such an object, imagine we need to design a system that sends emails. We won't implement the actual mechanism of sending them, we will just design a class that represents it.

An email may have the following properties:

  • An address (at least one is mandatory)
  • CC (optional)
  • Title (optional)
  • Body (optional)
  • Important flag (optional)

We can describe an email in our system as a data class:

data class Mail_V1(
    val to: List<String>,
    val cc: List<String>?,
  &...