将React上下文通过HOC传递给包装组件

Question

Is there a way that you can pass context through a React higher order component to a the component it wraps?

I have a HOC that receives context from its parent and utilizes that context to perform a basic, generalized action and then wraps a child component that also needs to access that same context to perform actions. Examples:

HOC:

export default function withACoolThing(WrappedComponent) {
  return class DoACoolThing extends Component {
    static contextTypes = {
      actions: PropTypes.object,
    }

    @autobind
    doAThing() {
      this.context.actions.doTheThing();
    }

    render() {
      const newProps = {
        doAThing: this.doAThing,
      };

      return (
        <WrappedComponent {...this.props} {...newProps} {...this.context} />
      );
    }
  }
};

Wrapped Component:

import React, { Component } from 'react';
import PropTypes from 'prop-types';
import { autobind } from 'core-decorators';
import withACoolThing from 'lib/hocs/withACoolThing';


const propTypes = {
  doAThing: PropTypes.func,
};

const contextTypes = {
  actions: PropTypes.object,
};

@withACoolThing
export default class SomeComponent extends PureComponent {

  @autobind
  doSomethingSpecificToThisComponent(someData) {
    this.context.actions.doSomethingSpecificToThisComponent();
  }

  render() {
    const { actions } = this.context;

    return (
      <div styleName="SomeComponent">
        <SomeOtherThing onClick={() => this.doSomethingSpecificToThisComponent(someData)}>Do a Specific Thing</SomeOtherThing>
        <SomeOtherThing onClick={() => this.props.doAThing()}>Do a General Thing</SomeOtherThing>
      </div>
    );
  }
}

SomeComponent.propTypes = propTypes;
SomeComponent.contextTypes = contextTypes;

Passing {...this.context} in the HOC does not work. this.context is an empty {} as long as the wrapped component is wrapped by the HOC. Please help? Is there any way to pass down context that doesn't involve passing it as props??

Answer 1

The Problem:

If contextTypes is not defined, then context will be an empty object.

The Solution:

Set WrappedComponent.contextTypes inside the HOC.

Explanation:

In the unfixed code, contextTypes for SomeComponent isn't being set. When SomeComponent gets decorated by @withACoolThing , any changes you make to SomeComponent are actually happening to DoACoolThing , and contextTypes for SomeComponent never gets set so it ends up being an empty object {} .

Side Note:

Because you are expanding this.context in the HOC and passing it down as props here:

<WrappedComponent {...this.props} {...newProps} {...this.context} />

You should have things like this.props.actions.doTheThing available in the child component.