React - Can A Child Component Send Value Back To Parent Form

React's one-way data-binding model means that child components cannot send back values to parent components unless explicitly allowed to do so. The React way of doing this is to pass down a callback to the child component (see Facebook's "Forms" guide).

class Parent extends Component {  constructor() {    this.state = {      value: ''    };  }  //...  handleChangeValue = e => this.setState({value: e.target.value});  //...  render() {    return (      <Child        value={this.state.value}        onChangeValue={this.handleChangeValue}      />    );  }}class Child extends Component {  //...  render() {    return (      <input        type="text"        value={this.props.value}        onChange={this.props.onChangeValue}      />    );  }}

Take note that the parent component handles the state, while the child component only handles displaying. Facebook's "Lifting State Up" guide is a good resource for learning how to do this.

This way, all data lives within the parent component (in state), and child components are only given a way to update that data (callbacks passed down as props). Now your problem is resolved: your parent component has access to all the data it needs (since the data is stored in state), but your child components are in charge of binding the data to their own individual elements, such as <input> tags.

Parent.js

import React, { Component } from 'react';import Child from './child'class Parent extends Component {  state = {    value: ''  }  onChangeValueHandler = (val) => {    this.setState({ value: val.target.value })  }  render() {    const { value } = this.state;    return (      <div>        <p> the value is : {value} </p>        <Child value={value} onChangeValue={this.onChangeValueHandler} />      </div>    );  }}export default Parent;

Child.js

  import React, { Component } from 'react';  class Child extends Component {  render() {  const { value , onChangeValue } = this.props;  return (    <div>      <input type="text"  value={value} onChange={onChangeValue}/>     </div>  );}}  export default Child;

you can see a live example on : https://codesandbox.io/s/two-way-binding-qq1o1?from-embed

You can add a "ref name" in your InputField so you can call some function from it, like:

<InputField    ref="userInput"   labelClass = "label"   labelText = "Username"   inputId = "signUp_username"   inputType = "email"   inputPlaceholder = "registered email"   inputClass = "input" />

So you can access it using refs:

this.refs.userInput.getUsernamePassword();

Where getUsernamePassword function would be inside the InputField component, and with the return you can set the state and call your props.handleSignUp