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

Factory Method

The Factory Method design pattern is all about creating objects.

But why do we need a method to create objects? Isn't that what constructors are for?

Well, constructors have limitations.

As an example, imagine we're building a game of chess. We would like to allow our players to save the state of the game into a text file and then restore the game from that position.

Since the size of the board is predetermined, we only need to record the position and type of each piece. We'll use algebraic notation for this – for example, the Queen piece at C3 will be stored in our file as qc3, the pawn piece at A8 will be stored as pa8, and so on.

Let's assume that we already read this file into a list of strings (which, by the way, would be an excellent application of the Singleton design pattern we discussed earlier).

Given the list of notations, we would like to populate our board with them:

// More pieces here
val notations = listOf...