NSUserInterfaceValidations
A protocol that a custom class can adopt to manage the enabled state of a UI element.
Declaration
protocol NSUserInterfaceValidationsOverview
The NSUserInterfaceValidations protocol works with the NSValidatedUserInterfaceItem protocol to allow the target of a user interface element such as a menu item or a toolbar item to decide whether or not the user interface element should be enabled.
Your custom classes should adopt this protocol if an instance may be the target of a user interface element and need to conditionally enable or disable the element based on the current state of the instance. For more details, read User Interface Validation.