# ExpressionFunctionPartialWithExtends

Canonical page: https://www.adaptabletools.com/docs/reference/expressionfunctionpartialwithextends

Partial custom function that inherits every unspecified field from
the system (or previously-registered custom) function named by `extends`.
Used by the expression-function override mechanism.

```ts title="TypeScript"
export interface AdaptableCustomExpressionFunctionWithExtends extends Partial<AdaptableCustomExpressionFunction> 
```

###### Extends

`Partial<`[`AdaptableCustomExpressionFunction`](https://www.adaptabletools.com/docs/reference/adaptablecustomexpressionfunction.md)`>`

## Properties

| Property | Type | Description |
| --- | --- | --- |
| [extends](https://www.adaptabletools.com/docs/reference/expressionfunctionpartialwithextends.md#extends) | `string` | Name of the function whose metadata to inherit (e.g. `'IS_BLANK'`). |

## Property Details

### extends

Name of the function whose metadata to inherit (e.g. `'IS_BLANK'`).

```ts title="TypeScript"
extends: string;
```

###### Property Value

`string`