如何创建一个元素并在反应中使用它对 append 子元素的引用？

Question

I'm trying to create a html element on a parent component on react and access that component div inside a child component, then I can append new elements in the div from the child component.

After many attempts I wasn't able to fix props.canvasDivElement.current = null on the child constructor.

I've tried to do this using REF and without refs... No luck so far.

Any ideas?

The parent component looks like:

import React from "react";
import ReactViewer from "../ReactViewer/ReactViewer";

export default class CanvasWrapper extends React.Component {
    private _divElement: React.RefObject<HTMLDivElement>;

    constructor(props: any) {
        super(props);
        this._divElement = React.createRef<HTMLDivElement>();
    }

    render() {
        return (
            <div>
                <ReactViewer canvasDivElement={this._divElement}></ReactViewer>
            </div>
        );
    }
}

The child component:

import React from "react";

type ReactViewerState = {
};

type ReactViewerProps = {
    canvasDivElement: React.RefObject<HTMLDivElement>;

};

    export default class ReactViewer extends React.Component<ReactViewerProps, ReactViewerState> {
        constructor(props: ReactViewerProps, state: ReactViewerState) {
            super(props, state);
            const newElement = document.createElement('span');
            newElement.innerText = 'element';
            props.canvasDivElement.current!.appendChild(newElement); //current is null
        }

        render() {
            return (
                <div ref={this.props.canvasDivElement} />
            );
        }
    }

Answer 1

It looks like you are trying to circumvent the basic principles of React to solve a problem that React provides other tools for. The React way of communicating between a child and a parent is to pass a callback function to the child. Then the child calls the callback to signal to the parent to update its children.

Answer 2

Rookie mistake, the element will always be null until it renders. I've changed the line bellow to the componentDidMount event:

    props.canvasDivElement.current!.appendChild(newElement);