React ForwardRef

What is Forward Ref

ForwardRef() is a utility function in react that let you expose a child components DOM to a parent component with a ref

Usually the parent component passes the props and data to the child component.

But in some instances like when working with input or where components need to respond with user interactions.

The parent components needs direct access to the child components DOM, to achieve this you can use forward refs

I will explain forward ref in more details along with examples below

const CoolComponent = forwardRef(render);

Let us take an example of a form component

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Create a new project and Exposing a DOM node to the parent component

create a new react js project in your computer and follow along

In your app.js file write the below code

import { useRef } from 'react';

export default function Form() {
  const ref = useRef(null);

  function handleClick() {
    ref.current.focus();
  }

  return (
    <form>
    </form>
  );
}

here we are importing useRef and creating a default functional component form

in the form create a const ref and initialize the useref with null

Now create a new file named CoolInput.js

In CoolInput.js write the below code there

import { forwardRef } from 'react';

const CoolInput = forwardRef(function CoolInput(props, ref) {
  const { label, ..otherProps } = props;
  return (
    <label>
      {label}
      <input {...otherProps} ref={ref} />
    </label>
  );
});

export default MyInput;

here we are importing the forwardref from react then we are wrapping the CoolInput function in the forwardref the ref is attached to the input elements ref attribute

Coming back to our app.js file add some additional code to it and it should look like this

import { useRef } from 'react';
import CoolInput from './input.js';

export default function Form() {
  const ref = useRef(null);

  function handleClick() {
    ref.current.focus();
  }

  return (
    <form>
      <CoolInput label="Type some text here:" ref={ref} />
      <button type="button" onClick={handleClick}>
        Edit
      </button>
    </form>
  );
}

Here we are adding a form and then we are passing the ref to the input.

Additionally we have created a button and attached its onClick to a handleClick function that focuses the on the text input when it is clicked.

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Testing the application

Here is what the application looks like

when you click on the edit button the input area comes into focus

The form component passes a ref to the CoolInput. CoolInput component then forwards that ref to the browsers input tag

As a result the form component can now control the browsers input tag and call input functions on it like focus

Forwarding refs through multiple components

You can forward the refs through multiple components as well. Let us take our example from above and refactor it to pass the refs through multiple components

Let us create a file call middle.js and there create a component called middle component

In the middle component file paste the below code

import React from 'react';
import CoolInput from './input';

const Middle = React.forwardRef(function middle(props, ref) {
  return (
    <div>
      <h2>Middle Component</h2>
      <CoolInput ref={ref} {...props} />
    </div>
  );
});

export default Middle;

Here we are importing react and importing CoolInput then we are wrapping our function middle inside of forwardref

Inside of our function middle we have CoolInput and we are passing our ref there to the CoolInput Component which in turns passes it to the browsers input

Let us open our App.js file and edit it and write the below code there

import { useRef } from 'react';
import Middle from './middle';

export default function Form() {
  const ref = useRef(null);

  function handleClick() {
    ref.current.focus();
  }

  return (
    <form>
      <Middle ref={ref} />
      <button type="button" onClick={handleClick}>
        Edit
      </button>
    </form>
  );
}

In the app.js we are referencing the Middle component and not the CoolInput component and thus we are passing the ref from the Form Component to the Middle component to the CoolInput Component and from the CoolInput Component to the browsers input element

this is how you can pass the refs through multiple components

Exposing an imperative handle instead of a DOM node

Sometimes you do not want to explore the whole DOM node / element to a component you just want to expose some function or api to the component

In our example above we just need the focus function of the browsers element in our parent component.

We do not need other functions the input element has like input.text etc

We can expose only the needed functions of the DOM element using an imperative handle

Let us learn more about imperative handle using an example

Let us refactor our above example to include just expose focus nad scrollInView functions of the input elements instead of the complete element

write the below code in the input.js file

import { React, forwardRef, useRef, useImperativeHandle } from 'react';

const CoolInput = forwardRef(function CoolInput(props, ref) {
    const inputRef = useRef(null);

    useImperativeHandle(ref, ()=> {
        return {
            focus(){
                inputRef.current.focus()
            },
            scrollIntoView(){
                inputRef.current.scrollIntoView();
            }
        }
    }, []);

    return <input {...props} ref={inputRef} />;

});

export default CoolInput;

We are importing forwardRef, useRef and useImperitiveHandle from react

we are initializing the useRef with null and assigning it to a inputRef const

then we are wrapping the CoolInput in the forwardRef function then we are calling the useImperitiveHandle function with ref as the prop and returning the focus and scrollIntoView functions

we also return the input ref with the input element

useImperitiveHandle is used to customize what value is passed using the ref to the parent component

The empty array is also passed as the third argument so that the custom api is only created once in a components lifecycle

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Common Pitfalls

a. Over-using refs

You should only use refs for situations where you cannot achieve the desired results using props

If you can use props instead of a ref, you should use the props

using refs increases app complexities

b. slowdown in performance

using refs causes increased re rendering of the components and slows down the application and hence they should only be used when necessary

c. Incompatibility with older versions of react

the refs are incompatible with older versions of react and hence cannot be used in older applications

d. maintenance of code and readability of code

refs cause readability and maintenance problems because they strech to multple files and you need to follow the tread and trace where this is leading

e.  Should not be used in higher order components

Higher order components should not use refs because it increase complexity and may cause hard to debug errors

refs should only be used in lower order components such as an input tag or an scroll view and should be designed to achieve a specific objective

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Forward Refs using Examples

Here are a few more examples of uising refs

WriteText.js file

import React from 'react';

const WriteText = React.forwardRef((props, ref) => {
  return <input ref={ref} type="text" {...props} />;
});

export default WriteText;

App.js

import React, { useRef } from 'react';
import WriteText from './WriteText';

function App() {
  const inputRef = useRef();

  const handleButtonClick = () => {
    inputRef.current.focus();
  };

  return (
    <div>
      <WriteText ref={inputRef} />
      <button onClick={handleButtonClick}>Elements in focus is Input</button>
    </div>
  );
}

export default App;

Here the WriteText components forwards the input element directly to the parent

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Example 2 : forwarding refs to an instance of a child component

Here we are going to expose a method of the child component to the parent component

The parent component can then call the function inside of the child component

import React, { useState, useImperativeHandle } from 'react';

const Calculator = React.forwardRef((props, ref) => {
  const [count, setCount] = useState(0);

  useImperativeHandle(ref, () => ({
    add: () => {
      setCount(count => count + 1);
    }
  }));

  return <div>Number: {count}</div>;
});

export default Calculator;

This is the calculator.js the child component file.

next we look at the App.js file

import React, { useRef } from 'react';
import Calculator from './Calculator';

function App() {
  const CalculatorRef = useRef();

  const handleButtonClick = () => {
    CalculatorRef.current.add();
  };

  return (
    <div>
      <Calculator ref={CalculatorRef} />
      <button onClick={handleButtonClick}>Add number</button>
    </div>
  );
}

export default App;

In the app.js we can cal the Calculator ref function Add() to add number to the count.

Thus in this way we can access the child components method from the parent component

ForwardRef Reference

forwardRef(render): You can call forwardRef(render) to let your component receive a ref and forward it to a child component

Parameters

render  the render funtion for your component. The react calls this render function with props and refs that the component received from its parent

The JSX will be return from your component. A component recieved from forwardRef can also recieve a ref prop

Return

forwardRef Returns a component that you can render in JSX

Caveats

In strict mode the react will call the render function twice. But if your render function is pure as it should be this should not affect the output of your component.

Conclusion

In this article we have leant what are react refs, how to use them

I hope you liked the article

Thanks for reading