# children A component that manages this object’s collection of children. ``` var children: any MDLObjectContainerComponent { get set } ``` ## Discussion Many asset formats describe a hierarchy of transforms that model the spatial relationships between meshes, lights, and cameras in the asset. In such formats, hierarchic transforms are [`MDLObject`](/documentation/ModelIO/MDLObject) instances whose [`children`](/documentation/ModelIO/MDLObject/children) property references the objects affected by the transform, and those objects can be other [`MDLObject`](/documentation/ModelIO/MDLObject) instances with children of their own. This property’s value is a component object—either a [`MDLObjectContainer`](/documentation/ModelIO/MDLObjectContainer) instance, or a custom class that adopts the [`MDLObjectContainerComponent`](/documentation/ModelIO/MDLObjectContainerComponent) protocol. By default, an object has no container component (that is, this property’s value is `nil`). To add a container component, either write to this property an instance of a container component class or call the [`addChild(_:)`](/documentation/ModelIO/MDLObject/addChild(_:)) method to create a default [`MDLObjectContainer`](/documentation/ModelIO/MDLObjectContainer) instance and add a child object to that container. > Note: > Reading or writing this property is equivalent to calling the ``doc://com.apple.modelio/documentation/ModelIO/MDLObject/componentConforming(to:)`` or ``doc://com.apple.modelio/documentation/ModelIO/MDLObject/setComponent(_:for:)`` method with the ``doc://com.apple.modelio/documentation/ModelIO/MDLObjectContainerComponent`` protocol. Container components support fast enumeration and subscripting, so you can treat an object’s children property similarly to an array. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)