React 无状态组件 this.refs..value？

Question

I don't know if I'm doing this correctly... If I want to get value from an input I use this.refs.whatever.value.trim() but if that input is a stateless function component how do I do retrieve the value onSubmit?

I know this isn't correct now after researching but how are you supposed to get value from these input fields?

import React, {Component} from 'react'

import {InputField} from '../components/forms/InputField'
import {Button} from '../components/forms/Button'

export default class SignupWrapper extends Component {
  _handleSubmit(e) {
    e.preventDefault();
    const email = this.refs.email.value.trim();
    const password = this.refs.password.value.trim();
    const confirm = this.refs.confirm.value.trim();
    console.log({email, password, confirm});
  }

  render() {
    return (
      <form id="application-signup" onSubmit={this._handleSubmit.bind(this)}>
        <InputField type={'email'} name={'email'} text={'email'}
                    helpBlock={'email is required'} ref="email" />
        <InputField type={'password'} name={'password'} text={'password'}
                    helpBlock={'password is required'} ref="password" />
        <InputField type={'password'} name={'confirm'} text={'confirm password'}
                    helpBlock={'password confirmation is required'} ref="confirm" />
        <Button type={'submit'} className={'btn btn-primary'} text={'signup'} />
      </form>
    )
  }
}

this is the stateless inputfield

import React from 'react'

export const InputField = (props) => (
  <div className="form-group col-xs-12">
    <label htmlFor={props.name}>{props.text}</label>
    <input type={props.type} name={props.name} className="form-control"
           data-stripe={props.stripe} />
    <span className="help-block">{props.helpBlock}</span>
  </div>
)

Answer 1

You can use ref s inside stateless components.

Here is also my example fiddle that shows you how it works.

import React from 'react'

export default ({ onChange }) => {
  let cityInput

  const onSubmit = e => {
    e.preventDefault()
    onChange(cityInput.value)
  }

  return (
    <form onSubmit={ onSubmit }>
      <input type='text' placeholder='Enter City Name'
        ref={ el => cityInput = el } />
      <button>Go!</button>
    </form>
  )
}

---

Note: Although this is one way to do it, however, this approach is not recommended unless you really need it. Try to think about more on redesigning your React code instead of hacking it like this. You may read more about it here .

Answer 2

as of react 16.8 you can use the useRef hook, from the docs :

useRef returns a mutable ref object whose .current property is initialized to the passed argument (initialValue). The returned object will persist for the full lifetime of the component.

function TextInputWithFocusButton() {
  const inputEl = useRef(null);
  const onButtonClick = () => {
    // `current` points to the mounted text input element
    inputEl.current.focus();
  };
  return (
    <>
      <input ref={inputEl} type="text" />
      <button onClick={onButtonClick}>Focus the input</button>
    </>
  );
}

Answer 3

Edit: Looks like this is not the issue anymore, since new ideas on how to handle this situation arose since this answer was written. Refer to inanc's answer instead of this one.

Refs are unavailable in stateless components. From React Docs :

Because stateless functions don't have a backing instance, you can't attach a ref to a stateless function component. Normally this isn't an issue, since stateless functions do not provide an imperative API. Without an imperative API, there isn't much you could do with an instance anyway. However, if a user wants to find the DOM node of a stateless function component, they must wrap the component in a stateful component (eg. ES6 class component) and attach the ref to the stateful wrapper component.

Answer 4

@inanc, show good method, but I propose an alternative way to use event target to get the DOM element reference. As you are using the form element, you can name your input elements and use it to access the form object.

const onSubmit = fn => e => {
  e.preventDefault()
  const city = e.target.city.value // Access elements through `form`
  if (city) {
    fn(city)
  }
}

const MyComponent = ({
  onChange
}) => {
  return ( 
    <div>
      <form onSubmit={onSubmit(onChange)}>
        <input type='text' name='city' placeholder='Enter City Name' />
        <button>Go!</button>
      </form>
    </div>
  )
}

Answer 5

Nowadays, you would want to avoid to use the ref attribute to get values from input fields. Instead you should use React's local state. The ref attribute is reserved for only a few use cases :

• Managing focus, text selection, or media playback
• Integrating with third-party DOM libraries
• Triggering imperative animations

Answer 6

You can't use refs in stateless react components (+1 to Moti Azu for his snippet from the documentation).

You can use multiple techniques to get stuff in/out of stateless components (without using Ref or use class components), I have created the snippet below to illustrate

1. How you can pass stuff into a stateless component (the label props set statically in the parent component).
2. How you can get stuff from a stateless component without use of refs (the input component)

try it out & let me know if you still have a problem, enjoy...

 // Stateless Component (just a <div> component with prop) const StatelessComponent = props => ( <div>{props.label}</div> ); // Stateless input Component const InputComponent = props => { return ( <input value={props.name} onChange={props.handleChange} /> ); }; // Parent Class Component class ParentComponent extends React.Component { state = { firstName: "HELCODE" }; handleChange = event => { this.setState({ firstName: event.target.value, }); }; render() { const {title} = this.props; console.log("rendered"); return ( <div> <h3>{title}</h3> <StatelessComponent label="This is a label passed to a stateless component as prop" /> <br/> <InputComponent name={this.state.firstName} handleChange={this.handleChange} /> <p>{this.state.firstName}{this.state.lastName} can read stuff from stateless components withough Ref using States</p> <br/> </div> ); } } // Render it ReactDOM.render( <ParentComponent title="Parent Component" />, document.getElementById("react") );

 <div id="react"></div> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>

Answer 7

just to add a solution for anyone that use react-semantic-ui.

https://react.semantic-ui.com/addons/ref

You can simply wrap the stateless functional component in this Ref component to retrieve the DOM node.

(very useful to deal with the scrolling position of a Sidebar.Pushable !)

Answer 8

import React, { useEffect, useRef } from 'react';

function TextFocusTest () {
  const textRef = useRef(null);

  useEffect(() => {
     textRef.current.focus();
  });

  return(
    <input ref{textRef} type="text">
  );

} 

export default TextFocusTest;