Скачать или смотреть Solve the React and Typescript Custom Hook Dilemma: Why Is Your API Call Executing Twice?

Discover effective solutions for handling API requests in `React` and `Typescript`, addressing issues like duplicate calls and type mapping.
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Solve the React and Typescript Custom Hook Dilemma: Why Is Your API Call Executing Twice?

In the dynamic world of web development, efficiently fetching data from APIs is crucial for building responsive and user-friendly applications. However, developers often encounter challenges when implementing API requests, especially with libraries like React and Typescript. One common issue is when an API call executes multiple times or the data structure doesn't match the expected type. This guide addresses such a scenario, providing clear solutions to these problems.

Understanding the Problem

A developer faced multiple issues within a custom API service hook using React and Typescript, specifically:

The API response was logged twice, leading to confusion.

Accessing the results from the service payload returned undefined even though the payload was an array.

The question arose from trying to type the results of the API call and enforce a specific data structure on the retrieved data, but facing challenges in validating the response.

Breaking Down the Solution

1. Identifying the API Call Execution Issue

One primary reason that the API call might execute twice is the way useEffect is set up. If not handled correctly, particularly without the appropriate dependency array, it can lead to unintended repeated executions of the function fetching data.

Solution:

Make sure that your useEffect is properly configured:

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2. Confirming the API Response Structure

The second issue was related to the type mapping of the API response. When logging data returned from the API, service.payload.results was undefined, despite service.payload logging as expected. The key here lies in understanding how you are setting the payload:

The original code sets payload to res.data directly. However, the developer expected payload to include a results property that contains the array of Visitor objects.

Solution:

You need to ensure that the res.data indeed has the structure you are expecting. If res.data only returns a list of visitors, you must restructure it accordingly:

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

Alternatively, if res.data already returns an object with results, ensure your interface correctly reflects that.

3. Implementing Type Safety with Type Guards

To avoid errors from unexpected data structures, you can use type guards. Type guards allow TypeScript to validate that the data conforms to the expected format before using it:

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4. Finalizing the Component Integration

In your component consuming this hook, ensure you check the status safely to avoid accessing properties that may not exist when the API call hasn’t completed yet:

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Conclusion

By understanding the nuances of React and Typescript, particularly when working with custom hooks and API requests, developers can efficiently troubleshoot common issues like multiple API calls and type safety errors. By ensuring proper use of useEffect, validating your data structures with type guards, and appropriately restructuring your API responses, you can create robust and error-free data-fetching components.

Happy coding!