react项目，传统类组件如何使用createRef()创建ref引用?

import React, { Component } from 'react'
export default class Child extends Component {
    constructor(props) {
        super(props);
        this.inputRef = React.createRef();
    }
    render() {
        return (
            <div className="Child">
                <input
                    type="text"
                    ref={this.inputRef}
                />
            </div>
        )
    }
}

this.inputRef = React.createRef();

<input type="text" ref={this.inputRef} />

if (this.inputRef.current) {
  console.log(this.inputRef.current.value);
}

this.inputRef.current.focus();

import React, { Component } from 'react'
export default class Child extends Component {
  constructor(props) {
    super(props);
    this.inputRef = React.createRef();
  }
  focusInput() {
    this.inputRef.current.focus();
  }
  getData() {
    if (this.inputRef.current) {
      console.log(this.inputRef.current.value);
    }
  }
  render() {
    return (
      <div className="Child">
        <input
          type="text"
          ref={this.inputRef}
          defaultValue="defaultValue"
          onChange={this.getData.bind(this)}
        />
        <input
          type="button"
          value="Focus the input"
          onClick={this.focusInput.bind(this)}
        />
      </div>
    )
  }
}

<input ref='target'/>

this.refs["target"].current.value

Warning: A string ref, "target", has been found within a strict mode tree. String refs are a source of potential bugs and should be avoided. We recommend using useRef() or createRef() instead. Learn more about using refs safely here: https://reactjs.org/link/strict-mode-string-ref

@deprecated ― https://reactjs.org/docs/refs-and-the-dom.html#legacy-api-string-refs
“refs”已弃用。ts(6385)