# partialAsync

Creates a modified copy of an object schema that marks all or only the selected entries as optional.

```ts
const Schema = v.partialAsync<TSchema, TKeys>(schema, keys);
```

## Generics

- `TSchema` <Property {...properties.TSchema} />
- `TKeys` <Property {...properties.TKeys} />

## Parameters

- `schema` <Property {...properties.schema} />
- `keys` <Property {...properties.keys} />

### Explanation

`partialAsync` creates a modified copy of the given object `schema` where all entries or only the selected `keys` are optional. It is similar to TypeScript's [`Partial`](https://www.typescriptlang.org/docs/handbook/utility-types.html#partialtype) utility type.

> Because `partialAsync` changes the data type of the input and output, it is not allowed to pass a schema that has been modified by the <Link href='../pipeAsync/'>`pipeAsync`</Link> method, as this may cause runtime errors. Please use the <Link href='../pipeAsync/'>`pipeAsync`</Link> method after you have modified the schema with `partialAsync`.

## Returns

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

## Examples

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

### Update user schema

Schema to update the user details.

```ts
import { isEmailAbsent, isUsernameAbsent } from '~/api';

const UserSchema = v.objectAsync({
  email: v.pipeAsync(
    v.string(),
    v.email(),
    v.checkAsync(isEmailAbsent, 'The email is already in the database.')
  ),
  username: v.pipeAsync(
    v.string(),
    v.nonEmpty(),
    v.checkAsync(isUsernameAbsent, 'The username is already in the database.')
  ),
  password: v.pipe(v.string(), v.minLength(8)),
});

const UpdateUserSchema = v.partialAsync(UserSchema);

/*
  { 
    email?: string;
    username?: string; 
    password?: string;
  }
*/
```

## Related

The following APIs can be combined with `partialAsync`.

### Schemas

<ApiList
  items={[
    'array',
    'exactOptional',
    'intersect',
    'lazy',
    'looseObject',
    'looseTuple',
    'map',
    'nonNullable',
    'nonNullish',
    'nonOptional',
    'nullable',
    'nullish',
    'object',
    'objectWithRest',
    'optional',
    'record',
    'set',
    'strictObject',
    'strictTuple',
    'tuple',
    'tupleWithRest',
    'undefinedable',
    'union',
  ]}
/>

### Methods

<ApiList
  items={[
    'assert',
    'config',
    'fallback',
    'forward',
    'getDefault',
    'getDefaults',
    'getFallback',
    'getFallbacks',
    'keyof',
    'message',
    'omit',
    'pick',
    'required',
    'unwrap',
  ]}
/>

### Actions

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

### Utils

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

### Async

<ApiList
  items={[
    'arrayAsync',
    'checkAsync',
    'exactOptionalAsync',
    'fallbackAsync',
    'forwardAsync',
    'getDefaultsAsync',
    'getFallbacksAsync',
    'intersectAsync',
    'lazyAsync',
    'looseObjectAsync',
    'looseTupleAsync',
    'mapAsync',
    'nonNullableAsync',
    'nonNullishAsync',
    'nonOptionalAsync',
    'nullableAsync',
    'nullishAsync',
    'objectAsync',
    'objectWithRestAsync',
    'optionalAsync',
    'parseAsync',
    'parserAsync',
    'partialCheckAsync',
    'rawCheckAsync',
    'rawTransformAsync',
    'recordAsync',
    'requiredAsync',
    'safeParseAsync',
    'safeParserAsync',
    'setAsync',
    'strictObjectAsync',
    'strictTupleAsync',
    'transformAsync',
    'tupleAsync',
    'tupleWithRestAsync',
    'undefinedableAsync',
    'unionAsync',
  ]}
/>