Book Image

Crystal Programming

By : George Dietrich, Guilherme Bernal
Book Image

Crystal Programming

By: George Dietrich, Guilherme Bernal

Overview of this book

Crystal is a programming language with a concise and user-friendly syntax, along with a seamless system and a performant core, reaching C-like speed. This book will help you gain a deep understanding of the fundamental concepts of Crystal and show you how to apply them to create various types of applications. This book comes packed with step-by-step explanations of essential concepts and practical examples. You'll learn how to use Crystal’s features to create complex and organized projects relying on OOP and its most common design patterns. As you progress, you'll gain a solid understanding of both the basic and advanced features of Crystal. This will enable you to build any application, including command-line interface (CLI) programs and web applications using IOs, concurrency and C bindings, HTTP servers, and the JSON API. By the end of this programming book, you’ll be equipped with the skills you need to use Crystal programming for building and understanding any application you come across.
Table of Contents (26 chapters)
1
Part 1: Getting Started
5
Part 2: Learning by Doing – CLI
10
Part 3: Learn by Doing – Web Application
13
Part 4: Metaprogramming
18
Part 5: Supporting Tools

Creating your own classes

Classes describe the behavior of objects. It is nice to learn that the standard types that come with Crystal are, for the most part, just ordinary classes you could have implemented on your own. Also, your application will need some more specialized classes, so let's create them.

New classes are created with the class keyword, followed by the name and then the definition of the class. The following a minimal example:

class Person
end
person1 = Person.new
person2 = Person.new

This example creates a new class named Person and then two instances of this class – two objects. This class is empty – it doesn't define any method or data, but Crystal classes come with some functionality by default:

p person1        # You can display any object and 
  # inspect it
p person1.to_s   # Any object can be transformed into
  # a String
p person1 == person2 ...