Book Image

Learn Kotlin Programming - Second Edition

By : Stephen Samuel, Stefan Bocutiu
Book Image

Learn Kotlin Programming - Second Edition

By: Stephen Samuel, Stefan Bocutiu

Overview of this book

Kotlin is a general-purpose programming language used for developing cross-platform applications. Complete with a comprehensive introduction and projects covering the full set of Kotlin programming features, this book will take you through the fundamentals of Kotlin and get you up to speed in no time. Learn Kotlin Programming covers the installation, tools, and how to write basic programs in Kotlin. You'll learn how to implement object-oriented programming in Kotlin and easily reuse your program or parts of it. The book explains DSL construction, serialization, null safety aspects, and type parameterization to help you build robust apps. You'll learn how to destructure expressions and write your own. You'll then get to grips with building scalable apps by exploring advanced topics such as testing, concurrency, microservices, coroutines, and Kotlin DSL builders. Furthermore, you'll be introduced to the kotlinx.serialization framework, which is used to persist objects in JSON, Protobuf, and other formats. By the end of this book, you'll be well versed with all the new features in Kotlin and will be able to build robust applications skillfully.
Table of Contents (21 chapters)
Free Chapter
1
Section 1: Fundamental Concepts in Kotlin
5
Section 2: Practical Concepts in Kotlin
15
Section 3: Advanced Concepts in Kotlin

Parameterized functions

Consider a function called random() that, when given some elements, returns one element randomly. We don't need to know what the types of the elements are when we write this function, as we will not be using the elements ourselves. We just need to be able to select one to return. When we use a type in this way—abstracting over the type, we use the term type parameter. So, our random function would have a single type parameter: the type of the elements we are selecting from.

If we want to write a generic function, such as the random function just mentioned, we might decide to start with something such as the following:

    fun random(one: Any, two: Any, three: Any): Any 

This would work as we can pass in any instances we choose. However, no matter what types we choose to pass in as arguments, our returned type would be inferred as Any. We&apos...