UNSUBSCRIBE statement

Cancels a subscription to an ABL named event. Specifically, the UNSUBSCRIBE statement cancels one or more subscriptions to one or more named events.

Note: ABL named events are completely different from the key function, mouse, widget, and direct manipulation events, which are described in the Handle-based Object Events Reference. They are also different from the class events described in the Class Events Reference.

Syntax

UNSUBSCRIBE [ PROCEDURE subscriber-handle ]
  [ TO ] { event-name | ALL } [ IN publisher-handle ]
PROCEDURE subscriber-handle

A procedure handle representing the subscriber to a named event.

The PROCEDURE option lets one procedure cancel a subscription on behalf of another. For example, if you want procedure A to cancel a subscription on behalf of procedure B, set subscriber-handle to the procedure handle of B.

If the PROCEDURE option does not appear, the AVM assumes that the subscriber is THIS-PROCEDURE, the procedure that contains the UNSUBSCRIBE statement.

event-name

A quoted string or character expression representing the name of a named event.

ALL

Cancels all subscriptions.

IN publisher-handle

A procedure handle representing the publisher of a named event.

If the IN option appears, the AVM cancels subscriptions to named events published by publisher-handle-specifically, either all subscriptions (if the ALL option appears), or only subscriptions to event-name (if event-name appears).

If the IN option does not appear, the AVM cancels subscriptions regardless of the publisher-specifically, either all subscriptions (if the ALL option appears), or only subscriptions to event-name (if event-name appears).

Example

For an example, see the reference entry for the PUBLISH statement.

Notes

See also

PUBLISH statement, PUBLISHED-EVENTS attribute, SUBSCRIBE statement, Unsubscribe( ) event method