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import React from 'react';
import { useForm, useWatch } from 'react-hook-form';
function useInputCache(values, causeField, effectField, callback) {
const [effectCache, setEffectCache] = React.useState(values[effectField]);
const evaluateRegStatus = (vals, currentState) => {
// check if field is registered (naive implementation for demonstration)
const isRegistered = !!vals[causeField];
return {
isRegistered,
registrationStatusChanged: isRegistered !== currentState,
hasValue: vals[effectField] !== undefined,
};
};
// use ref to track registration state across renders
const currentRegState = React.useRef(false);
React.useEffect(() => {
const { isRegistered, registrationStatusChanged, hasValue } =
evaluateRegStatus(values, currentRegState.current);
if (registrationStatusChanged && hasValue) {
if (isRegistered && !!effectCache) {
console.debug('Deploying cache');
callback(effectField, effectCache);
} else if (!isRegistered) {
console.debug('Caching before unmount');
setEffectCache(values[effectField]);
}
currentRegState.current = !!isRegistered;
}
// eslint-disable-next-line react-hooks/exhaustive-deps
}, [values, causeField, effectField, callback]);
}
export default function App() {
const { register, handleSubmit, setValue, control } = useForm({
mode: 'onChange',
defaultValues: {
name: '',
check: false,
optionalText: '',
},
});
const values = useWatch({
control,
});
useInputCache(values, 'check', 'optionalText', setValue);
return (
<div className="App">
<h1>Here's a form with conditional fields.</h1>
<form onSubmit={handleSubmit(console.log)}>
<input
name={'name'}
type={'text'}
ref={register({ required: true, min: 3 })}
placeholder={'Enter a name'}
/>
<br />
<label htmlFor={'check'}>
toggle field:
<input
name={'check'}
type={'checkbox'}
ref={register({ required: true })}
/>
</label>
<br />
{values.check && (
<input
name={'optionalText'}
ref={register({ required: false })}
placeholder={'Mandatory when check=true'}
/>
)}
</form>
</div>
);
}
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