How to Create a Generic Function in TypeScript that Accepts Multiple Fetch Functions

Learn how to enhance your TypeScript custom hooks to accept any number of generic fetch functions and return their responses effectively.
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How to Create a Generic Function in TypeScript that Accepts Multiple Fetch Functions

Introduction

As a React developer, you've likely encountered situations where you need to create custom hooks that handle different types of data fetching. A common requirement is to have a function that can handle multiple fetch functions and return their results as a structured response. This post will guide you through enhancing an existing TypeScript custom React hook to accept any number of fetch functions, returning their respective data types efficiently.

Understanding the Problem

Imagine you have a custom hook named useFetchMultipleDataMunicipio. Currently, this function only accommodates two fetch functions as parameters. The goal is to extend this hook's functionality, allowing it to accept any number of fetch functions while returning an appropriately structured tuple of responses, alongside other auxiliary variables.

The original implementation looks something like this:

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

Solution Overview

To transform this function, we can utilize TypeScript generics and rest parameters. Below, we'll break down the solution into manageable components.

Step 1: Define the Generic Fetch Function Type

First, we need to establish a type that represents our fetch functions:

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

This type allows us to clearly define the structure expected from each fetch function.

Step 2: Create a Response Type Mapping

Next, we need a utility type that extracts the response types from the array of fetch functions:

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

This type leverages TypeScript's capabilities to infer response types for each function dynamically.

Step 3: Updating the Hook to Accept Multiple Fetch Functions

Now, we can redefine our hook to accommodate any number of fetch functions:

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

Explanation of the Updated Hook

Rest Parameters: The ...args: T syntax allows the function to accept a variable number of fetch functions.

Structured Response: The returned data tuple's structure is dynamically typed based on the fetch functions provided.

Conclusion

By extending your custom React hook in this way, you can easily manage multiple asynchronous fetch operations, making your components more versatile and clean. Implementing TypeScript generics greatly enhances type safety, ensuring that the responses from various fetch functions align perfectly with your component's expectations.

Now you're equipped to build more powerful and flexible hooks in TypeScript! Feel free to share your thoughts and any additional modifications you might consider in the comments below.