Thinking in React Query

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In this talk, I'll explain React Query from a different perspective. After having maintained React Query for over two years and having answered many questions (often the same ones multiple times), I feel like there might be a fundamental understanding missing about the lib. I'll start with a quick introduction about my journey into open source and how I got to know React Query, followed by showing which mindset change is beneficial when working with React Query - how to "think in React Query". 

I'll have 3 major takeaways: 

1) React Query is not a data fetching library It's an async state manager, we'll quickly talk about what makes a state manager, why React Query is one and what "async state" means. 

2) staleTime is your best friend I've seen a bit of confusion about how to use React Query as a state manager, so I'll explain why setting staleTime is mostly all you need 

3) parameters are dependencies This is important to understand to show the boundaries between client state and server state, and is essential when doing state management with React Query I will then end with a note on "separation of concerns" and about the tradeoffs of just calling `useQuery` wherever you need it in your component tree.

This talk has been presented at React Summit 2023, check out the latest edition of this React Conference.

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FAQ

Adding parameters to the query key ensures entries are cached separately, avoids race conditions, enables automatic refetches when filters change, and prevents issues with stale closures.

No, React Query does not fetch data. It relies on a query function that returns a promise, which can be fulfilled by any data fetching library such as Axios, Fetch, or GraphQL Request.

React Query uses a unique query key to define the part of the state you're subscribing to, ensuring updates are efficient. It also offers selectors for fine-grained subscriptions to derived or computed results.

Stale time defines the time until data goes stale. It helps control how often React Query re-fetches data, preventing overfetching while keeping data up to date.

React Query can be used directly with useQuery wherever needed, eliminating the need to sync state with other managers like local state or Redux. This keeps React Query as the single source of truth.

React Query automatically re-fetches data on window focus, component mount, network reconnection, and query key changes, but only if the data is considered stale.

Client-state dependencies, such as filters, can be managed with local state or a global state manager like Zustand. React Query focuses on server state, allowing flexibility in managing client state.

You can create a simple query function that returns a resolved promise to demonstrate the issue without needing to expose your private API.

When creating the loop, make sure to pull the shoelace toward yourself first, then pull it through the gap. This small difference will result in a knot that will stay horizontal and won't come loose as easily.

React Query is an async state manager, not a data fetching library. It helps manage server state and keeps your data up to date automatically.

Dominik Dorfmeister
Dominik Dorfmeister
22 min
06 Jun, 2023

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Video Summary and Transcription
React Query is not a data fetching library, but an Asian state manager. It helps keep data up to date and manage agent life cycles efficiently. React Query provides fine-grained subscriptions and allows for adjusting stale time to control data fetching behavior. Defining stale time and managing dependencies are important aspects of working with React Query. Using the URL as a state manager and Zustand for managing filters in React Query can be powerful.
Available in Español: Pensando en React Query

1. Introduction to React Query and Misconceptions

Short description:

Most people don't know that there is a right and a wrong way to tie your shoes. When working with React Query, a lot of questions showed an underlying misconception of what React Query is or does. React Query is not a data fetching library. It doesn't do any data fetching for you. The query function only cares if you're returning a fulfilled or rejected promise.

Hello, everyone. Thanks for being here today, where I want to talk about tying your shoes correctly. Most people don't know that there is a right and a wrong way to tie your shoes. Both ways look very similar at first glance, but one knot is stable and the other loosens as you walk. It's a little difference that might change your life. Stay tuned until the end while I show you that trick.

When working with React Query, we might face similar situations, where a small tweak can make a huge difference. I discovered this when I started my open source journey back in 2020, where I was mostly helping out by engaging with the community. I answered a lot of questions on different platforms, which was a great way for me to get started in open source. Turns out people are really happy and grateful if you help them solve their problem. And I also learned a lot by having to look at situations I haven't encountered myself before. With that, I got to know React Query pretty well, and that's when I realized a common pattern among those questions. A lot of them showed an underlying misconception of what React Query is or does and would probably answer themselves with a little shift in thinking.

My name is Dominik and I'm a software engineer from Vienna. I go by the name TK-Dodo online almost everywhere. I work as a front-end tech lead at Edverity and I've also had the privilege to maintain the open-source library React Query for the past two years. So today, what I really want to talk about is showing you three simple ways on how to approach React Query with a better mindset. Similar to tying your shoes correctly, once you know it, it hopefully makes a lot of sense and is quite simple to follow. So let's take a look what it takes to be thinking in React Query.

The first point might surprise you, but it's true. Even though it's often described as the missing piece for data fetching in React, React Query is not a data fetching library. It doesn't do any data fetching for you, because if we take a quick look at a standard React Query example, we can see that we need to provide two things to the UseQuery hook. A unique query key, where React Query will store the data for us, and a query function that will be executed whenever data should be retrieved. We can then, of course, use that hook in a component to render data and the various states the query can be in. But if we take a quick look at the query function again, we can see that in this example, it's implemented with Axios, because why not? But the point is, that is your data fetching library. That query doesn't care how you do it. The only thing it cares about is if you're returning a fulfilled or rejected promise. In fact, and this is probably me talking as a library maintainer, if you're filing an issue telling me you can't show a reproduction because your API is private, I'll likely be telling you that this is the simplest way to implement the query function. No data fetching at all. All we're doing is return a resolved promise.

2. React Query: Data Fetching and State Management

Short description:

React Query doesn't fetch data, it's an Asian state manager. State is split by kind, not where it's used. React Query helps keep data up to date and manage agent life cycles. It's a specialized tool for the job. React Query makes state available efficiently.

Of course, React Query goes very well with data fetching libraries like Axios, Fetch or GraphQL Request because they all produce promises. Once we understand that React Query doesn't fetch data, it hopefully becomes clear that a whole class of questions around data fetching just disappear. Questions like how can I define a base URL with React Query? How can I access response headers with it? Or how can I make GraphQL requests with React Query? All questions around data fetching usually have the same answer. React Query doesn't care. Just somehow return a promise, please.

Okay, once we got that it's only fair to ask, if React Query is no data fetching library, then what is it? My answer to this question has always been an Asian state manager. Now it's important to understand what we mean by Asian state. Tanner Lindsley, the creator of React Query, gave a great talk in May 2020 called It's Time to Break Up with Your Global State. The talk is still very relevant today, so please watch it if you haven't already. The gist of it is that we have, for the longest time, sliced our state into where we need it to live. Do we only need it in one component? We'll probably start out by using local state. Do we need it available higher up the tree? Then we move it up, and potentially pass data down again as props. Do we need it even higher up, or everywhere in our application? We'll likely move it to a global state manager, like Redux or Zustand, which lives outside of React and then distributes it globally to our application. And we've been doing this for all kinds of state, no matter if it's the toggle button we're clicking in our app, or the list of issues we have to fetch over the network. We've treated them all exactly the same. The shift in thinking comes when we split state differently. Not where it is used, but by what kind of state it is. Because state that we own completely, that is synchronously available and always up to date, like when I click that dark mode toggle button, has totally different needs than state that is persisted remotely and asynchronously available, like a list of issues. With aging state or server state, we only see a snapshot in time of when we fetched it. It can get out of date because we are not the only owner of that state. The backend, probably our database, owns it. We have just borrowed it to display that snapshot. You might notice this when you leave a browser tab open for some time and then come back to it. Wouldn't it be nice to automatically see fresh and accurate data? That means we have to keep it up to date somehow because other users can make changes in the meantime as well. And because state is not synchronously available, meta information around that state, like loading and error states, need to be managed as well. So, keeping your data up to date automatically and managing agent life cycles isn't something you would get or need from a traditional all purpose state manager. But since we have a tool that is geared towards agent state, we can make all that happen and more. We just need to use the right tool for the right job.

The second part we need to understand is what a state manager is and why React Query is one. What state managers usually do is making your state available in your app efficiently.

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