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NSKeyValueObserverMBS class

Type Topic Plugin Version macOS Windows Linux iOS Targets
class Cocoa MBS MacBase Plugin 13.1 ✅ Yes ❌ No ❌ No ✅ Yes All
The Plugin class to use a key value observer.

The NSKeyValueObserving (KVO) informal protocol defines a mechanism that allows objects to be notified of changes to the specified properties of other objects.

You can observe any object properties including simple attributes, to-one relationships, and to-many relationships. Observers of to-many relationships are informed of the type of change made — as well as which objects are involved in the change.

NSObject provides an implementation of the NSKeyValueObserving protocol that provides an automatic observing capability for all objects. You can further refine notifications by disabling automatic observer notifications and implementing manual notifications using the methods in this protocol.

This class implements an observer with event for use in Xojo.

Change Kind Constants.

Constant Value Description
kChangeInsertion 2 Indicates that an object has been inserted into the to-many relationship that is being observed.
kChangeRemoval 3 Indicates that an object has been removed from the to-many relationship that is being observed.
kChangeReplacement 4 Indicates that an object has been replaced in the to-many relationship that is being observed.
kChangeSetting 1 Indicates that the value of the observed key path was set to a new value. This change can occur when observing an attribute of an object, as well as properties that specify to-one and to-many relationships.

Option Constants

Constant Value Description
kOptionInitial 4 If specified, a notification should be sent to the observer immediately, before the observer registration method even returns. more
kOptionNew 1 Indicates that the change dictionary should provide the new attribute value, if applicable.
Available in OS X v10.3 and later.
kOptionOld 2 Indicates that the change dictionary should contain the old attribute value, if applicable.
Available in OS X v10.3 and later.
kOptionPrior 8 Whether separate notifications should be sent to the observer before and after each change, instead of a single notification after the change. more

This class has no sub classes.

Some examples using this class:

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The items on this page are in the following plugins: MBS MacBase Plugin.


NSKeyedUnarchiverMBS   -   NSLayoutManagerMBS


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