Скачать или смотреть How to Retrieve State Variables from a Child Component in React 16.8 Using Hooks

Learn how to effectively `manage state` in React by lifting state up from a child component to a parent component, ensuring proper data flow and access in React 16.8.
---
This video is based on the question https://stackoverflow.com/q/64568685/ asked by the user 'Pm Rivière' ( https://stackoverflow.com/u/7237293/ ) and on the answer https://stackoverflow.com/a/64568842/ 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: Get state variable from child component using React 16.8^ coding style

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

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Retrieve State Variables from a Child Component in React 16.8 Using Hooks

When working with React, especially in the context of React 16.8 and beyond, utilizing hooks to manage state can be a bit tricky when multiple components are involved. A common scenario surfaces when a parent component needs to access or read a state variable that is defined in a child component. This post will break down how to effectively manage this situation and get your applications up and running smoothly.

The Problem

Imagine you have a parent component, MyPage, that needs to read a state variable defined in its child component, MyComponent. You might think that you could log this state variable directly, but the structure of React's component tree and state management logic means that isn't possible without additional steps.

Here is an outline of the initial code structure you might have:

MyPage.js

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

MyComponent.js

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

The console log in MyPage will throw an error because stateVariable is not defined there. So, how can we make it accessible? The answer lies within lifting state up.

The Solution: Lifting State Up

When multiple components need access to the same slice of state, the best practice is to move the state to a common ancestor of those components. Here’s how you can revise the code to achieve this:

Step 1: Move useState to MyPage

By managing the state in the parent component, MyPage, you can pass the state variable and its setter function down to MyComponent as props.

Updated MyPage.js

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

Step 2: Accept Props in MyComponent

Now that you have passed stateVariable and setStateVariable to MyComponent, you can use them there directly.

Updated MyComponent.js

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

Key Takeaways

State Management Hierarchy: In a React application, always lift state to the nearest common ancestor when multiple components need access to the same state.

Passing Props: Make use of React’s props feature to send state and state-setters down to child components.

Clearer Logic: Managing state at a higher level simplifies the relationship between components and helps to maintain a cleaner codebase.

By using hooks effectively and understanding how to manage state across components, you can enhance the functionality of your React applications significantly. This method not only solves the current problem but also prepares you for better practices in future projects.