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

Top-level functions

In addition to member functions and local functions, Kotlin also supports declaring top-level functions. These are functions that exist outside of any class, object, or interface and are defined directly inside a file. The name "top-level" comes from the fact that functions are not nested inside any structure and so they are at the top of the hierarchy of classes and functions.

Top-level functions are especially useful for defining helper or utility functions. It does not necessarily make sense to group them with other functions or create them when the contained object adds no value. In Java, these kinds of functions exist as static functions inside the helper classes. An example would be the functions of collections in the Java standard library.

However, some functions are so standalone that it makes little sense to take the trouble of creating a...