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# systemLayoutFittingSizeDidChange(forChildContentContainer:)

Notifies the container that a child view controller was resized using Auto Layout.

```
func systemLayoutFittingSizeDidChange(forChildContentContainer container: any UIContentContainer)
```

## Parameters

`container`

The child view controller that received the resizing message.

## Discussion

This method is called when a view controller that doesn’t use Auto Layout has a child view controller that uses Auto Layout and the child view controller is resized. When the child view controller responds to the [`systemLayoutSizeFitting(_:)`](/documentation/UIKit/UIView/systemLayoutSizeFitting(_:)) method, the [`systemLayoutFittingSizeDidChange(forChildContentContainer:)`](/documentation/UIKit/UIContentContainer/systemLayoutFittingSizeDidChange(forChildContentContainer:)) method is sent to the parent view controller.

---

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