[React] Use the new React Context API

Posted Answer1215

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了[React] Use the new React Context API相关的知识,希望对你有一定的参考价值。

The React documentation has been warning us for a long time now that context shouldn‘t be used and that the API is unstable. Well, with the release of React 16.3, we‘re finally getting a stable context API and what‘s even better is that it has received a makeover and the dev experience is fantastic! In this lesson, we‘ll look at an example app that passes props down several levels deep into the component tree and replace all that prop drilling with the new context API. We‘ll see how to create a Provider and a Consumer, how to use them in the code and we‘ll take a look at how the default properties that get passed into createContext come into play.

 

A condition that we need ‘context‘ API is to avoid pass Props all the way down to the component tree.

For example:

 

 

So porps are passed all the way down from 

  PageWrapper

          -- ProfileWrapper

      -- ProfileDetails

 

New context API looks like this:

1. Create an Context service:

import { createContext } from "react";

const ProfileContext = createContext({
  firstName: "Sally",
  lastName: "Anderson"
});

export const ProfileProvider = ProfileContext.Provider;

export const ProfileConsumer = ProfileContext.Consumer;

 ‘createContext‘ takes an default value. 

 

2. Wrap the top level component into Provider:

import { ProfileProvider } from "./ProfileContext";

  render() {
    return (
      <ProfileProvider value={this.state.profile}>
        <PageWrapper />
      </ProfileProvider>
    );
  }

 

If you want to just use default value, don‘t provide the Provider... this approach is a little bit strange.

  render() {
    return (
      <PageWrapper /> // may change in release
    );
  }

 

3. Remove all the props passed down.

4. In the component which do need context, use Consumer, Cunsumer takes a function as child.

import React from "react";
import { ProfileConsumer } from "./ProfileContext";

export const ProfileDetails = props => (
  <ProfileConsumer>
    {context => (
      <div>
        <div>
          <strong>First name:</strong> {context.firstName}
        </div>
        <div>
          <strong>Last name:</strong> {context.lastName}
        </div>
      </div>
    )}
  </ProfileConsumer>
);

 

以上是关于[React] Use the new React Context API的主要内容,如果未能解决你的问题,请参考以下文章

[React] Use the URL as the source of truth in React

[React] Use the React Effect Hook in Function Components

[React] Use React.ReactNode for the children prop in React TypeScript components and Render Props(代码

[React Router v4] Use the React Router v4 Link Component for Navigation Between Routes

React Cannot use JSX unless the ‘--jsx‘ flag is provided.

React Cannot use JSX unless the ‘--jsx‘ flag is provided.