didApplyConstraints

didApplyConstraints is a method in the Auto Layout system of Apple's UIKit framework, used in iOS and tvOS development. It is part of the UIViewController class and is called after the view controller's view has been laid out subviews. This method provides an opportunity for view controllers to perform additional layout adjustments or animations based on the constraints that have been applied to the view hierarchy.

The method signature is as follows:

swift

override func didApplyConstraints()

Developers can override this method in their custom view controllers to implement custom layout behavior. This can be useful for scenarios where the standard Auto Layout constraints are not sufficient to achieve the desired layout, or when additional animations are needed to transition between different layouts.

It's important to note that didApplyConstraints is called after the constraints have been applied, but before the view is drawn. This means that any changes made in this method will not be immediately visible, but will be taken into account in the next layout pass.

Additionally, didApplyConstraints is not called if the view controller's view is not part of a visible view hierarchy. This means that if the view controller is not currently being displayed, this method will not be called.

In summary, didApplyConstraints is a powerful tool for developers to fine-tune their layouts and animations in a view controller, providing a hook into the Auto Layout system at a critical point in the layout process.