Скачать или смотреть How to Fix the Issue of createContext Returning Default Value in React Context

Learn how to ensure your React context passes the correct values by wrapping your components properly in Next.js applications.
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This video is based on the question https://stackoverflow.com/q/73760196/ asked by the user 'Fukumi' ( https://stackoverflow.com/u/16693027/ ) and on the answer https://stackoverflow.com/a/73760293/ provided by the user 'Viktor Luft' ( https://stackoverflow.com/u/15090924/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When working with React, especially in conjunction with frameworks like Next.js, managing state across components can become challenging. One common issue developers encounter is when using the Context API—specifically, the createContext function appears to return default values instead of the intended values. This can lead to confusion and frustration as you attempt to get your application to behave correctly.

In this post, we'll explore a specific case in which a developer faced this problem while trying to set theme values across different components. We'll then break down how you can fix this issue by properly structuring your application.

Understanding the Problem

The first step to addressing the issue is recognizing why it happens. In the case presented, the developer was trying to create a context to manage a theme settings. The context was created and initialized, but when using the context in child components, it returned the default value rather than the dynamically set value.

The Situation:

A ThemeContext was created to manage theme settings (light or dark themes) across components.

The problem arose when the child components accessed this context via the useContext hook, resulting in them returning the initial default value "light" even after attempts to change it.

Solution Breakdown

Context Providers and Their Locations

The key to resolving this issue lies in understanding where the context provider needs to be placed in the application's structure.

The Wrong Approach

The context provider was used in the _document.tsx file:

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

However, _document.tsx is primarily used to customize the HTML document structure and is not intended for managing dynamic content or state. Consequently, the value passed to the provider was not updating as the state changed.

The Correct Approach

Instead, you should define the context provider in the _app.tsx file. This file is responsible for initializing pages and runs on both server and client sides, making it an ideal location to wrap your components with a context provider.

Step-by-Step Implementation

Create a new _app.tsx file in your Next.js project if it doesn’t exist already.

Write the Context and Provider in _app.tsx:

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

Use the Context in Child Components:
Now your child components can properly access and update the theme context.

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

Conclusion

By simply moving the context provider to the _app.tsx file, you ensure that it properly manages the state across the entire application. This change helps to eliminate the issue of the context returning default values, allowing your components to respond dynamically based on user interactions.

Understanding where and how to use context providers is crucial to effectively utilizing the Context API in React. If you find yourself stuck with similar state management issues, remember to look at how your providers are set up, as it could save you a lot of time and confusion.

With this solution, you are now equipped to manage theme states or similar requirements seamlessly across your React application. Happy coding!