`useRHFShouldUnregister()`

useRHFShouldUnregister is a polyfill for the deprecated shouldUnregister option in React Hook Form v7. It automatically unregisters unmounted fields. It takes a form ref, unregister and the optional 'keep state' options object that is applied to all unmounted fields.

It is important that the fields that should unregister be provided their default values via the defaultValue/defaultChecked prop instead of via useForm.

Installation

npm install use-rhf-should-unregister

Usage

import { useRef } from 'react';
import { useForm } from 'react-hook-form';
import { useRHFShouldUnregister } from 'use-rhf-should-unregister';

type PersonalDetails = {
  firstName: string;
  lastName: string;
  hasPet: boolean;
  petName?: string;
};

const App = () => {
  const formRef = useRef<HTMLFormElement>(null);
  const { handleSubmit, unregister, watch } = useForm<PersonalDetails>({
    defaultValues: {
      firstName: 'Aaron',
      lastName: 'Cook',
      hasPet: false,
    },
  });

  useRHFShouldUnregister<PersonalDetails>(formRef, unregister, {
    keepDirty: true,
    keepTouched: true,
  });

  const onSubmit = (data: Partial<PersonalDetails>) => console.log(data);

  const hasPet = watch('hasPet');

  return (
    <form onSubmit={handleSubmit(onSubmit)} ref={formRef}>
      <label htmlFor='firstName'>First name</label>
      <input {...register('firstName', { required: true })} />

      <label htmlFor='lastName'>Last name</label>
      <input {...register('lastName', { required: true })} />

      <label htmlFor='hasPet'>Do you have a pet?</label>
      <input type='checkbox' {...register('hasPet')} />

      {hasPet && (
        <>
          <label htmlFor='petName'>Pet name</label>
          <input
            {...register('petName', { required: true })}
            defaultValue='Max'
          />
        </>
      )}

      <input type='submit' />
    </form>
  );
};

export default App;

Alternatives

As an alternative to using useRHFShouldUnregister, you can create your own custom input component that calls unregister in the useEffect cleanup.

import { TextField } from '@material-ui/core';
import { useEffect } from 'react';
import {
  FormProvider,
  useController,
  useForm,
  useFormContext,
} from 'react-hook-form';

export const ShouldUnregisterInput = ({
  name,
  register,
  unregister,
  shouldUnregister = false,
  keepStateOptions = {},
  defaultValue,
}) => {
  useEffect(() => {
    return () => {
      if (!shouldUnregister) return;
      // Unregister input on unmount
      unregister(name, keepStateOptions);
    };
  }, [shouldUnregister, unregister]);

  return <input {...register(name)} defaultValue={defaultValue} />;
};

export const ShouldUnregisterControlledInput = ({
  name,
  shouldUnregister = false,
  keepStateOptions = {},
  defaultValue,
}) => {
  const { unregister } = useFormContext();

  useEffect(() => {
    return () => {
      if (!shouldUnregister) return;
      // Unregister TextField on unmount
      unregister(name, keepStateOptions);
    };
  }, [shouldUnregister, unregister]);

  const {
    field: { ref, ...inputProps },
  } = useController({
    name,
    // defaultValue should be sent instead via props
  });

  return (
    <TextField inputRef={ref} {...inputProps} defaultValue={defaultValue} />
  );
};

const App = () => {
  const { handleSubmit, register, unregister } = useForm();

  const onSubmit = (data) => console.log(data);

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <FormProvider {...methods}>
        <ShouldUnregisterInput
          name='firstName'
          defaultValue='Aaron'
          shouldUnregister
          register={register}
          unregister={unregister}
          keepStateOptions={{ keepDirty: true }}
        />
        <ShouldUnregisterControlledInput
          name='lastName'
          defaultValue='Cook'
          shouldUnregister
          keepStateOptions={{ keepDirty: true }}
        />
      </FormProvider>
    </form>
  );
};

export default App;