Book Image

Hands-On Design Patterns with Kotlin

By : Alexey Soshin
Book Image

Hands-On Design Patterns with Kotlin

By: Alexey Soshin

Overview of this book

Design patterns enable you as a developer to speed up the development process by providing you with proven development paradigms. Reusing design patterns helps prevent complex issues that can cause major problems, improves your code base, promotes code reuse, and makes an architecture more robust. The mission of this book is to ease the adoption of design patterns in Kotlin and provide good practices for programmers. The book begins by showing you the practical aspects of smarter coding in Kotlin, explaining the basic Kotlin syntax and the impact of design patterns. From there, the book provides an in-depth explanation of the classical design patterns of creational, structural, and behavioral families, before heading into functional programming. It then takes you through reactive and concurrent patterns, teaching you about using streams, threads, and coroutines to write better code along the way By the end of the book, you will be able to efficiently address common problems faced while developing applications and be comfortable working on scalable and maintainable projects of any size.
Table of Contents (13 chapters)

Chunked

It's very common to see this chunking logic in production code.

You have a huge list of identifiers that you read from somewhere and you need to check whether your database or some remote service contains them. But there are limitations on how many identifiers you can pass with a single request. Databases, for example, often have limitations of the number of arguments to a query and on the total query length:

fun dbCall(ids: List<Int>) {
if (ids.size > 1000) {
throw RuntimeException("Can't process more than 1000 ids")
} // Does something here
}

We can't simply pass an entire list to our function:

// That will fail at runtime
dbCall(hugeList)

So, we write large piles of imperative code:

val pageSize = 1000
val pages = hugeList.size / pageSize

for (i in 0..pages) {
val from = i * pageSize
val p = (i+1) * pageSize
val...