Resolving the Issue of Async Function Always Returning the Same Data in React Native

Learn how to fix the issue of async functions returning stale data by implementing cache-control headers in your React Native app.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Async function always returns the same data

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Async Function Always Returns the Same Data in React Native: How to Fix It

In the world of React Native development, fetching data asynchronously is a common task. However, developers often run into frustrating situations where an async function appears to return the same data irrespective of updates made in the backend. In this guide, we will explore one such issue where the getProductById function returns stale data even after updating the "like" status of a product. Let’s break down the problem and find an effective solution.

The Problem at Hand

You have a product screen that fetches data using the getProductById function, which is called when the screen mounts. The issue arises when you press a button that updates the product’s "like" status, and then attempts to fetch the product data again. Instead of obtaining the updated data, the old data is still returned. Here's a summary of the workflow:

Fetching Product Data: The getProductById method is called once upon mounting the screen.

Updating "Like" Status: When the "like" button is pressed, the like status is updated.

Re-fetching Data: After updating the like status, you call getProductById again to refresh the product data, but it returns the old value.

What could possibly be going wrong?

Identifying the Core Issue

The core of this problem lies in caching. Upon making the fetch request, the data is often cached, leading to the async function pulling the already cached response instead of the updated one. This is especially common in applications that rely on robust performance, where caching is utilized for efficiency.

Symptoms of the Problem

The getProductById function returns updated data on the initial mount but not after changing the like status.

Even calls from other functions or buttons do not yield the expected current data but instead return outdated information.

A delay in receiving updates is observed (the fresh data appears only after some time).

The Solution: Implementing Cache-Control Headers

To rectify this issue, you need to inform your fetch request to bypass the cache and retrieve the latest data from the server. This can be achieved by adding a cache-control header in your fetch request, ensuring that the data is not retrieved from a cached version.

Step-by-Step Implementation

Add Cache-Control Header: Modify your fetch request by appending a cache-control header. Below is an example of how to set it up:

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

Adjust Your Fetch Logic: Ensure that you are using these headers in your API calling functions, such as getProductById. Your function should be updated to include the headers as shown below:

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

Test the Implementation: After implementing the cache-control, test the app again. You should see that the getProductById function now returns the correct, updated data immediately after the like status is changed.

Conclusion

Facing issues with async functions returning stale data can be frustrating, but understanding and implementing cache-control headers can be an effective workaround. By ensuring that your fetch requests do not rely solely on cached data, you can create a smoother user experience with timely and relevant updates. Next time you encounter this problem, revisit your fetch requests and implement caching strategies like the one discussed in this post. Happy coding!