# Object Dropdown Knob

The object knob allows you to dynamically enter an object value for a widget property in the Widgetbook UI.
This is particularly useful for properties that require an object input, such as a user profile or an enum value.

## Variants

The object knob has two variants:

- `context.knobs.object.dropdown()`: This variant allows you to enter an object value via a dropdown menu. It does not accept `null` values.
- `context.knobs.objectOrNull.dropdown()`: This variant allows you to enter an object value via a dropdown menu or set the value to `null`. It is useful when the property can be optional.

<Info>
  Widgetbook also offers support for segmented button object knobs which are
  documented on the [Object Segmented Knob page](/knobs/object/segmented).
</Info>

## Properties

In addition to the knob's [base properties](/knobs/overview#properties), the object dropdown knob includes the following:

<Accordion title="context.knobs.object.dropdown()" defaultOpen>
  <Property name="options" type="T" required>
    The options shown in the dropdown menu. The type of the options must be the same as the type of the property.
  </Property>

  <Property name="labelBuilder" type="LabelBuilder<T>" optional>
    A function to format the options for display in the dropdown menu.
  </Property>
</Accordion>

## `context.knobs.object.dropdown()`

### Example

<iframe
  src="https://preview.widgetbook.io/#/?path=knobpreview/object-dropdown-knob&panels=knobs"
  width="100%"
  height="240px"
/>

### Usage

To use the object dropdown knob, call the `context.knobs.object.dropdown()` method.

```dart title="Example: Object Dropdown Knob"
@UseCase(type: MyWidget, name: 'Default')
Widget buildUseCase(BuildContext context) {
  return MyWidget(
    status: context.knobs.object.dropdown( // [!code highlight]
      label: 'status', // [!code highlight]
      labelBuilder: (value) => value!.name, // [!code highlight]
      options: [ // [!code highlight]
        OnlineStatusType.online, // [!code highlight]
        OnlineStatusType.offline, // [!code highlight]
        OnlineStatusType.busy, // [!code highlight]
      ], // [!code highlight]
    ), // [!code highlight]
  );
}

enum OnlineStatusType { online, offline, busy }
```

## `context.knobs.objectOrNull.dropdown()`

### Example

<iframe
  src="https://preview.widgetbook.io/#/?path=knobpreview/object-dropdown-nullable-knob&panels=knobs"
  width="100%"
  height="240px"
/>

### Usage

To use the nullable object dropdown knob, call the `context.knobs.objectOrNull.dropdown()` method.

```dart title="Example: Nullable Object Dropdown Knob"
@UseCase(type: MyWidget, name: 'Default')
Widget buildUseCase(BuildContext context) {
  return MyWidget(
    status: context.knobs.objectOrNull.dropdown(
      label: 'status',
      labelBuilder: (value) => value!.name,
      options: [
        OnlineStatusType.online,
        OnlineStatusType.offline,
        OnlineStatusType.busy,
      ],
    ),
  );
}

enum OnlineStatusType { online, offline, busy }
```

## Multi-snapshot Support

Multi-snapshot support for Widgetbook Cloud allows you to generate multiple screenshots of a single use case with varying values using [KnobsConfigs](/cloud/snapshots/multi-snapshot#multi-snapshot-for-knobs) and [AddonsConfigs](/cloud/snapshots/multi-snapshot#multi-snapshot-for-addons).
Please refer to the [ObjectKnobConfig page](/knobs/object/overview#multi-snapshot-support) for more information.