Mastering TypeScript with RTK Query: Overcoming Common Issues

Discover solutions for TypeScript issues when utilizing queryFn in RTK Query. Learn best practices and ensure your API calls are correctly typed!
---
This video is based on the question https://stackoverflow.com/q/73979994/ asked by the user 'topched' ( https://stackoverflow.com/u/1030730/ ) and on the answer https://stackoverflow.com/a/73982276/ provided by the user 'Linda Paiste' ( https://stackoverflow.com/u/10431574/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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: rtk-query typescript for custom queryFn on API endpoint

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Mastering TypeScript with RTK Query: Overcoming Common Issues

When working with React applications, managing API calls can become a challenge, especially when integrating TypeScript for type safety. One common issue arises when using the queryFn inside the API call with the RTK Query. Developers often face complaints from TypeScript about the return value of the queryFn. In this post, we will explore the problem, identify its root causes, and provide effective solutions to overcome it.

Understanding the Problem

In a typical scenario where you're using rtk-query, integrating TypeScript can lead to type mismatches. Here’s a basic outline of the important components involved:

Type Definitions: The TypeScript types for fetchBaseQuery are defined strictly, with the JSON data returned from the server being of type unknown, rather than any.

Return Types: Errors often occur concerning the required structure of the returned values from your queryFn.

For instance, consider the following code snippet that aims to fetch some fields based on feature flags:

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

In this setup, while the intent is correct, TypeScript raises an error regarding the return type of the queryFn, stating that the structure returned (an empty array) doesn't meet the expected type criteria.

Solution Breakdown

Let’s dive into the solutions step by step:

1. Use Type Assertions

To resolve the types issues, the first step is to use type assertions. When performing a base query, TypeScript expects you to define the return type explicitly:

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

This simple assertion informs TypeScript that the expected outcome will have the structure following Fields[].

2. Adjust Return Type in the Query Definition

Another core issue lies in how you define the getFields query. It’s important to clarify that the data returned should be directly the type you're working with. Here's the corrected declaration:

Instead of:

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

It should be written as:

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

3. Properly Handle the Response Structure

Your queryFn should comply with the expected structure of the return value. Instead of returning an empty array directly when the feature flag is false, it needs to balance the return structure properly:

When the feature flag is not enabled:

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

When returning the result from baseQuery:

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

4. Complete Working Code Example

With those adjustments made, your full working code should appear as follows:

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

Conclusion

Integrating TypeScript with RTK Query adds a layer of complexity, but by understanding the structure required by TypeScript and ensuring your return types are clear, you can navigate these errors with ease. Remember to leverage type assertions, properly define your query return types, and maintain the expected structures on return values. With these strategies, you'll find your TypeScript and RTK Query implementations are smoother and free of annoying type errors.

By addressing these common mistakes, you’ll greatly improve the maintainability and functionality of your code, ensuring a robust application development process.

Видео Mastering TypeScript with RTK Query: Overcoming Common Issues канала vlogize