# Derived property from function on objects

Add a new transform table column backed by a [Foundry function](../../functions/overview/index.md). The new column can be of type boolean, string, number, or time, depending on the output of the function.

To use a function in this transform, it must satisfy the following requirements:

* The function input parameters must include an `ObjectSet<ObjectType>` parameter (and can optionally include other input parameters).
* The function return type must be a `FunctionsMap<ObjectType, CustomType>`.
* The `FunctionsMap` keys are objects with object IDs matching those in the table.
* The `FunctionsMap` values are primitives.

See [Function-backed columns](../../workshop/widgets-object-table/index.md#function-backed-columns) for more information.

:::callout{theme="success" title="Best practice"}
When defining a function that returns a numerical value, we recommend returning either **Double** or **Integer** over **Float**.
:::

## Input type

String, number, time, boolean

## Output type

String

## Usage information

| Functionality | Availability |
| --- | --- |
| [Standard Quiver card](../core-concepts/index.md#cards) | Unsupported |
| [Transform table transform](../cards-transform-table/index.md) | Supported |