Book Image

State Management with React Query

By : Daniel Afonso
Book Image

State Management with React Query

By: Daniel Afonso

Overview of this book

State management, a crucial aspect of the React ecosystem, has gained significant attention in recent times. While React offers various libraries and tools to handle state, each with different approaches and perspectives, one thing is clear: state management solutions for handling client state are not optimized for dealing with server state. React Query was created to address this issue of managing your server state, and this guide will equip you with the knowledge and skills needed to effectively use React Query for state management. Starting with a brief history of state management in the React ecosystem, you’ll find out what prompted the split from a global state to client and server state and thus understand the need for React Query. As you progress through the chapters, you'll see how React Query enables you to perform server state tasks such as fetching, caching, updating, and synchronizing your data with the server. But that’s not all; once you’ve mastered React Query, you’ll be able to apply this knowledge to handle server state with server-side rendering frameworks as well. You’ll also work with patterns to test your code by leveraging the testing library and Mock Service Worker. By the end of this book, you'll have gained a new perspective of state and be able to leverage React Query to overcome the obstacles associated with server state.
Table of Contents (14 chapters)
Part 1: Understanding State and Getting to Know React Query
Part 2: Managing Server State with React Query

What is state in React?

State is the heart of your React application.

I challenge you to try to build a React application without any type of state. You’d probably be able to do something, but you would soon conclude that props cannot do everything for you and get stuck.

As mentioned in the introduction, state is a mutable data source used to store your data.

State is mutable, which means that it can be changed over time. When a state variable changes, your React component will re-render to reflect any changes that the state causes to your UI.

Okay, now, you might be wondering, “What will I store in my state?” Well, the rule of thumb that I follow is that if your data fits into any of the following points, then it’s not state:

  • Props
  • Data that will always be the same
  • Data that can be derived from other state variables or props

Anything that doesn’t fit this list can be stored in state. This means things such as data you just fetched through a request, the light or dark mode option of a UI, and a list of errors that you got from filling a form in the UI are all examples of what can be state.

Let’s look at the following example:

const NotState = ({aList = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10
  ]}) => {
  const value = "a constant value";
  const filteredList = aList.filter((item) => item % 2 ===
  return =>
    <div key={item}>{item}</div>);

Here, we have a component called NotState. Let’s look at the values we have in there and use our rule of thumb.

The aList variable is a component prop. Since our component will receive this, it doesn’t need to be state.

Our value variable is assigned a string value. Since this value will always be constant, then it doesn’t need to be state.

Finally, the filteredList variable is something that can be derived from our aList prop; therefore, it doesn’t need to be state.

Now that you are familiar with the concept of state, let’s get our hands dirty and understand how can we manage it in React.