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)

Let

Usually, we use let() to do something only if the object is not null:

val sometimesNull = if (Random().nextBoolean()) "not null" else null

sometimesNull?.let {
println("It was $it this time")
}

One common gotcha here is that let() by itself also works on nulls:

val alwaysNull = null

alwaysNull.let { // No null pointer there
println("It was $it this time") // Always prints null
}

Don't forget the question mark, ?, when you use let() for null checks.

The return value of let() is not related to the type it operates on:

val numberReturned = justAString.let {
println(it)
it.length
}

This code will print "string" and return Int 6 as its length.