How to Properly Re-render a Component in React Native with Async Functions

Learn the correct approach to re-render your components in React Native when dealing with async functions and state updates. Find out how to modify the `useEffect` hook to trigger data fetch on state changes!
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This video is based on the question https://stackoverflow.com/q/66526458/ asked by the user 'Kyle Lynch' ( https://stackoverflow.com/u/14183786/ ) and on the answer https://stackoverflow.com/a/66527099/ provided by the user 'jperl' ( https://stackoverflow.com/u/11758901/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Component Re-rendering in React Native

As a React Native developer, you may find yourself in a common situation: you want to change your component's state and observe that specific data being updated through an async function. In this guide, we will analyze a problem concerning re-rendering a component effectively when interacting with asynchronous data calls, especially when working with Firestore.

The Problem

Imagine you’ve created a component that retrieves posts based on the selected type of post (for example, "sitter" or "need sitter"). However, when you change the state of typeOfPost using button clicks, the async function responsible for fetching data does not get invoked again. This can be frustrating, especially when you want to see the updated data reflect immediately after changing the state.

The Initial Setup

Here’s a simplified breakdown of your component structure:

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

Within Component1, you utilize the useEffect hook, meant to trigger an async fetch to Firestore. However, you notice that it only executes once upon initial mount.

The Solution: Modifying useEffect

First, let's clarify why you weren't observing the desired behavior. The current implementation of useEffect specifies [] as its dependency array, which means it runs only once when the component is mounted. To make sure the getData function runs each time typeOfPost changes, you need to update the dependency array.

Updated useEffect

Here's how you can configure the useEffect hook correctly:

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

Complete Component1 Example

Here’s how the updated Component1 would look in its entirety:

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

Conclusion

By leveraging the useEffect hook correctly, you ensure that your async function fetches data every time the underlying state changes, enhancing both performance and user experience. React Native's component lifecycle can be tricky, but understanding how to manage the rendering process with state updates will go a long way in building responsive applications.

Happy coding! If you encounter similar issues or have any further questions, feel free to reach out in the comments below!

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