In the preceding chapter, you learned about the architectural principles of Flux. In particular, you used the Redux library to implement concrete Flux concepts in a React application. Having a framework of patterns like Flux in place, to help you reason about how state changes and flows through your application, is a good thing. At the end of the chapter, you learned about the potential limitations in terms of scale.

In this chapter, we are going to walk you through yet another approach to handling state in a React application. Like Redux, Relay is used with both web and mobile React applications. Relay relies on a language called GraphQL used to fetch resources and to mutate those resources.

The premise of Relay is that it can be scaled in ways that Redux and other approaches to handling state are limiting. It does this by eliminating them, and keeping the focus on the data requirements of the component.

In the final chapter of this book, you'll work on a React Native implementation of the ever popular Todo MVC application.