---
title: variantAsync
description: Creates a variant schema.
source: /schemas/variant/variantAsync.ts
contributors:
  - fabian-hiller
  - EltonLobo07
---

import { ApiList, Property } from '~/components';
import { properties } from './properties';

# variantAsync

Creates a variant schema.

```ts
const Schema = v.variantAsync<TKey, TOptions, TMessage>(key, options, message);
```

## Generics

- `TKey` <Property {...properties.TKey} />
- `TOptions` <Property {...properties.TOptions} />
- `TMessage` <Property {...properties.TMessage} />

## Parameters

- `key` <Property {...properties.key} />
- `options` <Property {...properties.options} />
- `message` <Property {...properties.message} />

### Explanation

With `variantAsync` you can validate if the input matches one of the given object `options`. The object schema to be used for the validation is determined by the discriminator `key`. If the input does not match a schema and cannot be clearly assigned to one of the options, you can use `message` to customize the error message.

> It is allowed to specify the exact same or a similar discriminator multiple times. However, in such cases `variantAsync` will only return the output of the first untyped or typed variant option result. Typed results take precedence over untyped ones.

> For deeply nested `variant` schemas with several different discriminator keys, `variant` will return an issue for the first most likely object schemas on invalid input. The order of the discriminator keys and the presence of a discriminator in the input are taken into account.

## Returns

- `Schema` <Property {...properties.Schema} />

## Examples

The following examples show how `variantAsync` can be used.

### Message schema

Schema to validate a message object.

```ts
import { isValidGroupReceiver, isValidUserReceiver } from '~/api';

const MessageSchema = v.objectAsync({
  message: v.pipe(v.string(), v.nonEmpty()),
  receiver: v.variantAsync('type', [
    v.objectAsync({
      type: v.literal('group'),
      groupId: v.pipeAsync(
        v.string(),
        v.uuid(),
        v.checkAsync(isValidGroupReceiver, 'The group cannot receive messages.')
      ),
    }),
    v.objectAsync({
      type: v.literal('user'),
      email: v.pipeAsync(
        v.string(),
        v.email(),
        v.checkAsync(isValidUserReceiver, 'The user cannot receive messages.')
      ),
    }),
  ]),
});
```

### User schema

Schema to validate unique user details.

```ts
import { isRegisteredEmail, isRegisteredUsername, isValidUserId } from '~/api';

const UserSchema = v.variantAsync('type', [
  // Assume this schema is from a different file and reused here.
  v.variantAsync('type', [
    v.objectAsync({
      type: v.literal('email'),
      email: v.pipeAsync(
        v.string(),
        v.email(),
        v.checkAsync(isRegisteredEmail, 'The email is not registered.')
      ),
    }),
    v.objectAsync({
      type: v.literal('username'),
      username: v.pipeAsync(
        v.string(),
        v.nonEmpty(),
        v.checkAsync(isRegisteredUsername, 'The username is not registered.')
      ),
    }),
  ]),
  v.objectAsync({
    type: v.literal('userId'),
    userId: v.pipeAsync(
      v.string(),
      v.uuid(),
      v.checkAsync(isValidUserId, 'The user id is not valid.')
    ),
  }),
]);
```

## Related

The following APIs can be combined with `variantAsync`.

### Schemas

<ApiList items={['looseObject', 'object', 'objectWithRest', 'strictObject']} />

### Methods

<ApiList items={['config', 'getDefault', 'getFallback']} />

### Actions

<ApiList
  items={[
    'brand',
    'check',
    'description',
    'entries',
    'flavor',
    'guard',
    'maxEntries',
    'metadata',
    'minEntries',
    'notEntries',
    'partialCheck',
    'rawCheck',
    'rawTransform',
    'readonly',
    'title',
    'transform',
  ]}
/>

### Utils

<ApiList items={['entriesFromList', 'isOfKind', 'isOfType']} />

### Async

<ApiList
  items={[
    'checkAsync',
    'fallbackAsync',
    'getDefaultsAsync',
    'getFallbacksAsync',
    'looseObjectAsync',
    'objectAsync',
    'objectWithRestAsync',
    'parseAsync',
    'parserAsync',
    'partialCheckAsync',
    'pipeAsync',
    'rawCheckAsync',
    'rawTransformAsync',
    'safeParseAsync',
    'safeParserAsync',
    'strictObjectAsync',
    'transformAsync',
  ]}
/>
