Available Value Transformers

In addition to providing a mechanism for registering your own value transformers, there are several built-in transformers provided by NSValueTransformer.

The built-in transformers provide facilities for negating boolean values, testing for nil or non nil values, and archiving and unarchiving values into NSData instances.

NSNegateBooleanTransformerName

The NSNegateBooleanTransformerName value transformer returns an instance of NSNumber containing a boolean value. The returned value is the boolean negation of the original value and is reversible.

This value transformer is useful in enabling or disabling user interface elements, as well as setting the values of checkboxes and radio buttons.

NSIsNilTransformerName

The NSIsNilTransformerName value transformer returns an instance of NSNumber containing a boolean value. The returned value is YES if the original value is nil, otherwise the returned value is NO. This value transformer is not reversible.

This value transformer is often used to enable or disable user interface elements.

NSIsNotNilTransformerName

The NSIsNotNilTransformerName value transformer returns an instance of NSNumber containing a boolean value. The returned value is YES if the original value is not nil, otherwise the returned value is NO. This value transformer is not reversible.

This value transformer is often used to enable or disable user interface elements.

NSUnarchiveFromDataTransformerName

The NSUnarchiveFromDataTransformerName transformer returns an object created by attempting to unarchive the data in the NSData object passed as the value. The reverse transformation returns an NSData instance created by archiving the value.

An object must implement the NSCoding protocol using sequential archiving in order to be unarchived and archived with this transformer.

This transformer is primarily used with instances of NSUserDefaultsController. This transformer allows your application to store objects in the user defaults that are not natively supported, for example, NSColor objects.

NSKeyedUnarchiveFromDataTransformerName

The NSKeyedUnarchiveFromDataTransformerName transformer returns an object created by attempting to unarchive the data in the NSData object passed as the value. The reverse transformation returns an NSData instance created by archiving the value.

This transformer differs from the NSUnarchiveFromDataTransformerName transformer in that the object must implement the NSCoding protocol using keyed archiving, rather than sequential archiving..

This transformer is primarily used with instances of NSUserDefaultsController. This transformer allows your application to store objects in the user defaults that are not natively supported, for example, NSColor objects.