Instance Method

willChange(_:valuesAt:forKey:)

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

Declaration

func willChange(_ changeKind: NSKeyValueChange, valuesAt indexes: IndexSet, forKey key: String)

Parameters

change

The type of change that is about to be made.

indexes

The indexes of the to-many relationship that will be affected by the change.

key

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

Discussion

Use this method when implementing key-value-observing 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 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 willChangeValue(forKey: String, withSetMutation: NSKeyValueSetMutationKind, using: Set<AnyHashable>)

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

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