Instance Method

willChangeValue(forKey:withSetMutation:using:)

Informs the observed object that the specified change is about to be made to a specified unordered to-many relationship.

Declaration

func willChangeValue(forKey key: String, withSetMutation mutationKind: NSKeyValueSetMutationKind, using objects: Set<AnyHashable>)

Parameters

key

The name of a property that is an unordered to-many relationship

mutationKind

The type of change that will be made.

objects

The objects that are involved in the change (see NSKeyValueSetMutationKind).

Discussion

Use this method when implementing key-value observer compliance manually.

Special Considerations

You rarely need to override this method in subclasses, but if you do, be sure to call super.

See Also

Notifying Observers of Changes

func willChangeValue(forKey: String)

Informs the observed object that the value of a given property is about to change.

func didChangeValue(forKey: String)

Informs the observed object that the value of a given property has changed.

func willChange(NSKeyValueChange, valuesAt: IndexSet, forKey: String)

Informs the observed object that the specified change is about to be executed at given indexes for a specified ordered to-many relationship.

func didChange(NSKeyValueChange, valuesAt: IndexSet, forKey: String)

Informs the observed object that the specified change has occurred on the indexes for a specified ordered to-many relationship.

func didChangeValue(forKey: String, withSetMutation: NSKeyValueSetMutationKind, using: Set<AnyHashable>)

Informs the observed object that the specified change was made to a specified unordered to-many relationship.

Beta Software

This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.

Learn more about using Apple's beta software