React refs

1.React.createRef()

class CustomTextInput extends React.Component {
  constructor(props) {
    super(props);
    this.textInput = React.createRef();
  }
  render() {
    return (
      <div>
        <input
          type="text"
          ref={this.textInput} />
      </div>
    );
  }
}

1. React.createRef可以给Dom元素添加ref。
2. React.createRef可以给Class组件添加ref。
3. React.createRef不能给函数式组件使用！！

回调Refs

class CustomTextInput extends React.Component {
  constructor(props) {
    super(props);
    this.textInput = null;
    this.setTextInputRef = element => {
      this.textInput = element;
    };
  }

  render() {
    return (
        <input
          type="text"
          ref={this.setTextInputRef}
        />
    );
  }
}