How to Use an async Database Call with useState() and useEffect() in React

Learn how to effectively fetch data asynchronously in React using `useState()` and `useEffect()`. Get practical solutions to replace undefined variables with your fetched data!
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How to Use an async Database Call with useState() and useEffect() in React

Fetching data from a database is a common requirement in web applications. However, using hooks like useState() and useEffect() in React to manage asynchronous data fetching can sometimes lead to issues, such as variables remaining undefined. If you've encountered this problem, you're not alone. Let's break down how to properly use an async database call with useState() and useEffect() to avoid these issues.

The Problem

You may find yourself in a situation where you've set up your data fetching function and are using the useState() hook to store the data. Unfortunately, after every re-render, the variable that should hold your data remains undefined. This can happen when you incorrectly handle the asynchronous nature of your database calls.

Example Code Snippet

Here's a common setup that causes issues:

[[See Video to Reveal this Text or Code Snippet]]

In this example, the getMyThing function is called synchronously to set the initial state, which doesn't allow the component to wait for the async operation to finish, resulting in myThing being set to undefined.

The Solution

To properly manage asynchronous data fetching in React:

Initial State Setup

Set the initial state of myThing to null, allowing it to be updated later.

Using useEffect for Side Effects

Fetch the data inside the useEffect hook, which is designed for executing side effects like fetching data.

Updated Code Example

Here's how you can structure your component correctly:

[[See Video to Reveal this Text or Code Snippet]]

Alternative Approach Without Async/Await

If you're not comfortable using async/await, you can also use Promises directly:

[[See Video to Reveal this Text or Code Snippet]]

Important Considerations

Dependencies Array: The [id] in the dependencies array of useEffect is crucial. It determines when the data fetching effect runs. If id changes, useEffect will be triggered again to fetch the new data.

Async Logic Only in useEffect: Avoid executing asynchronous logic in useState() or other parts of the code. It can lead to unexpected results since these functions aren't designed to handle promises.

Conclusion

Using async database calls in React requires careful handling to avoid undefined states after re-renders. By using useEffect() effectively to manage your asynchronous actions and keeping your state up-to-date, you can ensure your components behave as expected. Remember to manage your dependencies carefully, and your application will be better equipped to handle real-world data fetching scenarios.

By following the guidelines provided above, you’ll eliminate the confusion around using useState() and useEffect() with asynchronous calls and enhance the overall reliability of your React components.