# useApplyMetafieldsChange

Returns a function to mutate the `metafields` property of the checkout.

## 

### UseApplyMetafieldsChangeGeneratedType

Returns a function to mutate the `metafields` property of the checkout.

#### Returns: (change: MetafieldChange) => Promise<MetafieldChangeResult>
export function useApplyMetafieldsChange<
  Target extends RenderExtensionTarget = RenderExtensionTarget,
>(): (change: MetafieldChange) => Promise<MetafieldChangeResult> {
  const api = useApi<Target>();

  if ('applyMetafieldChange' in api) {
    return api.applyMetafieldChange;
  }

  throw new ExtensionHasNoMethodError(
    'applyMetafieldChange',
    api.extension.target,
  );
}


### MetafieldRemoveChange

Removes a metafield.

### type

value: `"removeMetafield"`

  - Metafield: export interface Metafield {
  /**
   * The name of the metafield. It must be between 3 and 30 characters in
   * length (inclusive).
   */
  key: string;

  /**
   * A container for a set of metafields. You need to define a custom
   * namespace for your metafields to distinguish them from the metafields
   * used by other apps. This must be between 2 and 20 characters in length (inclusive).
   */
  namespace: string;

  /**
   * The information to be stored as metadata.
   */
  value: string | number;

  /** The metafield’s information type. */
  valueType: 'integer' | 'string' | 'json_string';
}
The type of the `MetafieldRemoveChange` API.

### key

value: `string`

The name of the metafield to remove.

### namespace

value: `string`

The namespace of the metafield to remove.

### Metafield

Metadata associated with the checkout.

### key

value: `string`

The name of the metafield. It must be between 3 and 30 characters in
length (inclusive).

### namespace

value: `string`

A container for a set of metafields. You need to define a custom
namespace for your metafields to distinguish them from the metafields
used by other apps. This must be between 2 and 20 characters in length (inclusive).

### value

value: `string | number`

The information to be stored as metadata.

### valueType

value: `"string" | "integer" | "json_string"`

The metafield’s information type.

### MetafieldUpdateChange

Updates a metafield. If a metafield with the
provided key and namespace does not already exist, it gets created.

### type

value: `"updateMetafield"`

  - Metafield: export interface Metafield {
  /**
   * The name of the metafield. It must be between 3 and 30 characters in
   * length (inclusive).
   */
  key: string;

  /**
   * A container for a set of metafields. You need to define a custom
   * namespace for your metafields to distinguish them from the metafields
   * used by other apps. This must be between 2 and 20 characters in length (inclusive).
   */
  namespace: string;

  /**
   * The information to be stored as metadata.
   */
  value: string | number;

  /** The metafield’s information type. */
  valueType: 'integer' | 'string' | 'json_string';
}
The type of the `MetafieldUpdateChange` API.

### key

value: `string`

The name of the metafield to update.

### namespace

value: `string`

The namespace of the metafield to add.

### value

value: `string | number`

The new information to store in the metafield.

### valueType

value: `"string" | "integer" | "json_string"`

The metafield’s information type.

### MetafieldRemoveCartChange

Removes a cart metafield.

### type

value: `"removeCartMetafield"`

  - Metafield: export interface Metafield {
  /**
   * The name of the metafield. It must be between 3 and 30 characters in
   * length (inclusive).
   */
  key: string;

  /**
   * A container for a set of metafields. You need to define a custom
   * namespace for your metafields to distinguish them from the metafields
   * used by other apps. This must be between 2 and 20 characters in length (inclusive).
   */
  namespace: string;

  /**
   * The information to be stored as metadata.
   */
  value: string | number;

  /** The metafield’s information type. */
  valueType: 'integer' | 'string' | 'json_string';
}
  - CartMetafield: export interface CartMetafield {
  /** The key name of a metafield. */
  key: string;

  /** The namespace for a metafield. */
  namespace: string;

  /** The value of a metafield. */
  value: string;

  /** The metafield's type name. */
  type: string;
}
The type of the `MetafieldRemoveChange` API.

### key

value: `string`

The name of the metafield to remove.

### namespace

value: `string`

The namespace of the metafield to remove.

### CartMetafield

Represents a custom metadata attached to a resource.

### key

value: `string`

The key name of a metafield.

### namespace

value: `string`

The namespace for a metafield.

### value

value: `string`

The value of a metafield.

### type

value: `string`

The metafield's type name.

### MetafieldUpdateCartChange

Updates a cart metafield. If a metafield with the
provided key and namespace does not already exist, it gets created.

### type

value: `"updateCartMetafield"`

  - Metafield: export interface Metafield {
  /**
   * The name of the metafield. It must be between 3 and 30 characters in
   * length (inclusive).
   */
  key: string;

  /**
   * A container for a set of metafields. You need to define a custom
   * namespace for your metafields to distinguish them from the metafields
   * used by other apps. This must be between 2 and 20 characters in length (inclusive).
   */
  namespace: string;

  /**
   * The information to be stored as metadata.
   */
  value: string | number;

  /** The metafield’s information type. */
  valueType: 'integer' | 'string' | 'json_string';
}
  - CartMetafield: export interface CartMetafield {
  /** The key name of a metafield. */
  key: string;

  /** The namespace for a metafield. */
  namespace: string;

  /** The value of a metafield. */
  value: string;

  /** The metafield's type name. */
  type: string;
}
The type of the `MetafieldUpdateChange` API.

### metafield

value: `{ key: string; namespace: string; value: string; type: string; }`


### MetafieldChangeResultSuccess

### type

value: `"success"`

The type of the `MetafieldChangeResultSuccess` API.

### MetafieldChangeResultError

### type

value: `"error"`

The type of the `MetafieldChangeResultError` API.

### message

value: `string`

A message that explains the error. This message is useful for debugging.
It is **not** localized, and therefore should not be presented directly
to the buyer.

## Related

- [StandardApi](https://shopify.dev/docs/api/checkout-ui-extensions/apis/standardapi)
- [CheckoutApi](https://shopify.dev/docs/api/checkout-ui-extensions/apis/checkoutapi)
- [OrderStatusApi](https://shopify.dev/docs/api/checkout-ui-extensions/apis/orderstatusapi)
- [CartLineItemApi](https://shopify.dev/docs/api/checkout-ui-extensions/apis/cartlineitemapi)
- [PickupPointListApi](https://shopify.dev/docs/api/checkout-ui-extensions/apis/pickuppointlistapi)
- [PickupLocationListApi](https://shopify.dev/docs/api/checkout-ui-extensions/apis/pickuplocationlistapi)
- [ShippingOptionItemApi](https://shopify.dev/docs/api/checkout-ui-extensions/apis/shippingoptionitemapi)
- [ExtensionTargets](https://shopify.dev/docs/api/checkout-ui-extensions/apis/extensiontargets)