How to set focus a ref using React-Hook-Form

Question

How do you implement set focus in an input using React-Hook-Form, this is what their FAQ's "How to share ref usage" code here https://www.react-hook-form.com/faqs/#Howtosharerefusage

import React, { useRef } from "react";
import { useForm } from "react-hook-form";

export default function App() {
  const { register, handleSubmit } = useForm();
  const firstNameRef = useRef();
  const onSubmit = data => console.log(data);

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input name="firstName" ref={(e) => {
        register(e)
        firstNameRef.current = e // you can still assign to ref
      }} />
      <input name="lastName" ref={(e) => {
        // register's first argument is ref, and second is validation rules
        register(e, { required: true })
      }} />

      <button>Submit</button>
    </form>
  );
}

I tried set focusing the ref inside useEffect but it doesn't work:

useEffect(()=>{
   firstNameRef.current.focus();
},[])

Neither does inside the input:

<input name="firstName" ref={(e) => {
    register(e)
    firstNameRef.current = e;
    e.focus();
}} />

Answer 1

You can set the focus using the setFocus helper returned by the useForm hook (no need to use a custom ref):

 const allMethods = useForm();
 const { setFocus } = allMethods;

 ...

 setFocus('inputName');

https://react-hook-form.com/api/useform/setFocus