2017-23 @ Fabio Franchino

Call child method from parent React.js component

Posted on January 28, 2021 in
2 min read

In this sample I wanted to figure out how to call from within a parent component a child component' method in a React.js app.

I wanted to explore both the Class and Functional version as well.

The parent wrapper

Here the parent code:

import CChild from './CChild'
import FChild from './FChild'

function Mock (props) {
  const fref = useRef()
  const cref = useRef()

  const handleClick = e => {
    fref.current.setFromOutside('HELLO from Parent')
    cref.current.setFromOutside('HELLO from Parent')
  }
  return (
    <div>
      <button onClick={handleClick}>Show Me!</button>
      <FChild ref={fref} />
      <CChild ref={cref} />
    </div>
  )
}

There are two children components and a button to trigger the call.

The method setFromOutside belongs to the children definition.

The children components

Here the code of the Class version:

import React from 'react'

class Child extends React.Component {
  constructor (props) {
    super(props)
    this.state = { message: 'Waiting' }
  }

  setFromOutside (msg) {
    this.setState({ message: msg })
  }

  render () {
    return (
      <h1>{this.state.message}</h1>
    )
  }
}
export default Child

The Class version is pretty straighforward, the method setFromOutside is public, thus, it's visible from the parent by means of the child reference.

Here the Functional version:

import { useState, forwardRef, useImperativeHandle } from 'react'

function Child (props, ref) {
  const [message, setMessage] = useState('Waiting')

  useImperativeHandle(ref, () => ({
    setFromOutside (msg) {
      setMessage(msg)
    }
  }), [])

  return (
    <h1>{message}</h1>
  )
}

export default forwardRef(Child)

Well, in this implementation there are some notable things to say:

  • The public method needs to be included in the useImperativeHandle hook.
  • Also, you have to export the component with forwardRef HOC function.
  • By exporting the component with forwardRef, the Function now has two arguments, props and ref, where the latter needs to be used in useImperativeHandle hook.

Ouch, that's not really "natural" to me, but still.

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