Book Image

Hands-On Reactive Programming with Clojure - Second Edition

By : Konrad Szydlo, Leonardo Borges
Book Image

Hands-On Reactive Programming with Clojure - Second Edition

By: Konrad Szydlo, Leonardo Borges

Overview of this book

Reactive Programming is central to many concurrent systems, and can help make the process of developing highly concurrent, event-driven, and asynchronous applications simpler and less error-prone. This book will allow you to explore Reactive Programming in Clojure 1.9 and help you get to grips with some of its new features such as transducers, reader conditionals, additional string functions, direct linking, and socket servers. Hands-On Reactive Programming with Clojure starts by introducing you to Functional Reactive Programming (FRP) and its formulations, as well as showing you how it inspired Compositional Event Systems (CES). It then guides you in understanding Reactive Programming as well as learning how to develop your ability to work with time-varying values thanks to examples of reactive applications implemented in different frameworks. You'll also gain insight into some interesting Reactive design patterns such as the simple component, circuit breaker, request-response, and multiple-master replication. Finally, the book introduces microservices-based architecture in Clojure and closes with examples of unit testing frameworks. By the end of the book, you will have gained all the knowledge you need to create applications using different Reactive Programming approaches.
Table of Contents (15 chapters)

State, identity, and value

Many programs operate on states. For example, the following Java class introduces a Car object:

class Car {
public String type;
public String color;
public int age;
}

public Car (String type, String color, int age) {
this.type = type;
this.color = color;
this.age = age;
}

Car sedan = new Car("Sedan", "red", 5);

Programs written in many languages, such as Java, C#, Ruby, or Python, are full of similar classes. We are so used to this approach that we rarely consider how problematic it can be.

We created an instance of Car, represented by a particular type, sedan. We might have bought this car when it was already five years old. The car can exist in many states—as a brand new car with an age of 1, or as an antique car with an age of over 25. At each point in time, the car has precisely one valid state. Its state might...