use-validated-state

Manages state with validation

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Usage

The use-validated-state hook validates state with a given rule each time the state is set. It returns an object with the current validation state, last valid value, and current value:

import { useValidatedState } from '@mantine/hooks';

const [{ lastValidValue, value, valid }, setValue] =
  useValidatedState('valid', (state) => state === 'valid');

lastValidValue; // -> valid
value; // -> valid
valid; // -> true

setValue('invalid');

lastValidValue; // -> valid
value; // -> invalid
valid; // -> false

Example

Your email

Current value: [empty string]

Last valid value: [empty string]

import { TextInput, Text, Box } from '@mantine/core';
import { useValidatedState } from '@mantine/hooks';

function Demo() {
  const [{ value, lastValidValue, valid }, setEmail] = useValidatedState(
    '',
    (val) => /^\S+@\S+$/.test(val),
    true
  );

  return (
    <Box maw={320} mx="auto" style={{ overflowWrap: 'break-word' }}>
      <TextInput
        value={value}
        onChange={(event) => setEmail(event.currentTarget.value)}
        withAsterisk
        error={!valid}
        placeholder="email@example.com"
        label="Your email"
      />

      <Text size="sm" mt="md">
        <Text inherit c="dimmed" component="span">
          Current value:
        </Text>{' '}
        {value || '[empty string]'}
      </Text>

      <Text size="sm">
        <Text inherit c="dimmed" component="span">
          Last valid value:
        </Text>{' '}
        {lastValidValue || '[empty string]'}
      </Text>
    </Box>
  );
}

Definition

interface UseValidatedStateValue<T> {
  /** Current value */
  value: T;

  /** Last valid value */
  lastValidValue: T | undefined;

  /** True if the current value is valid; false otherwise */
  valid: boolean;
}

type UseValidatedStateReturnValue<T> = [
  /** Current value */
  UseValidatedStateValue<T>,
  /** Handler to update the state, passes `value` and `payload` to `onChange` */
  (value: T) => void,
];

function useValidatedState<T>(
  initialValue: T,
  validate: (value: T) => boolean,
  initialValidationState?: boolean,
): UseValidatedStateReturnValue<T>

Exported types

The UseValidatedStateValue and UseValidatedStateReturnValue types are exported from @mantine/hooks;

import type { UseValidatedStateValue, UseValidatedStateReturnValue } from '@mantine/hooks';

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