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)

Exercises

In this exercise, we will modify the om-pm project we created in the previous section. The objective is to add keyboard shortcuts so that power users can operate the agile board more efficiently.

The shortcuts to be supported are as follows:

  • The up, down, left, and right arrow keys: These allow the user to navigate through the cards, highlighting the current one
  • The n and p keys: These are used to move the current card to the next (right) or previous (left) column, respectively

The key insight here is to create a new core.async channel, which will contain keypress events. These events will then trigger the actions that were outlined previously. We can use the Google Closure library to listen for events. Just add the following require to the application namespace:

(:require [goog.events :as events]) 

Then, use the following function to create a channel from DOM events...