Method ActiveXObject():isEventSubscribed() Foundation

Determines whether a COM/ActiveX event has been subscribed to.

:isEventSubscribed( <cName> | <nDISPID> ) --> lReturn
<cName> is a character string that specifies the name of the COM/ActiveX event.
<nDISPID> is a numeric value that specifies the dispatch ID (DISPID) of the event to be fired. This parameter may be used as an alternative to parameter <cName>.

:isEventSubscribed() returns a logical value. If the class implements event handling of any kind for the COM/ActiveX event specified, :isEventSubscribed() returns the value .T. (true). If no event handler is defined for processing the event, the method returns .F. (false).


Method :isEventSubscribed() can be used by an application to determine whether the ActiveXObject is ready to process a specific COM/ActiveX event.

If a value greater zero is returned by :isEventSubscribed(), the COM/ActiveX event has been subscribed and can be handled by the object. Event handling logic can be provided either through the methods implemented by a class derived from ActiveXObject, or via a code block assigned to the corresponding instance variable (callback slot).

A COM/ActiveX event can be subscribed to either by the class designer or at the application level. In the former case, the designer of a class derived from ActiveXObject implements a method that has the same name as a COM/ActiveX event. The framework automatically calls this method when the corresponding COM/ActiveX event is fired by the ActiveX object connected. The method implicitly becomes the default event handler for the event. In order to implement event handling on the application level, a callback code block must be assigned to the event's callback slot (instance variable). ActiveXObject also provides the method :subscribeEvent() which offers a low-level interface for binding logic to a certain COM/ActiveX event.

If either of these approaches is used, the COM/ActiveX event is subscribed to by the ActiveObject instance and method :isEventSubscribed() returns the value .T. (true).


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