react refs

componentDidMount () {
    console.log(this.refs.father)
  }
 render () {
    return (
      <div>
        <div ref="father"></div>
      </div>
    )
  }

componentDidMount () {
    console.log(this.father)
  }
 render () {
    return (
      <div>
        <div ref={(ref) => {this.father = ref}}></div>
      </div>
    )
  }