Try OpenEdge Now
skip to main content
ABL Reference
Class Events Reference : Defining multiple handlers for an event

Defining multiple handlers for an event

If you need to subscribe more than one event handler for an ABL class event, when you publish the event, any OUTPUT or INPUT-OUTPUT parameter you define returns the value set by the final event handler to execute. In addition, any INPUT-OUTPUT parameter you define passes the value set by one event handler as input to the next event handler to execute. A similar effect occurs if you pass a handle or object reference as an INPUT parameter and your event handlers set the value of a public data member on the handle or class-based object. The returned value of the input object data element is the value set by the final handler to execute for the event. In addition, the order of execution for multiple handlers subscribed to a single event is not guaranteed, making it difficult or impossible to know exactly how parameter values returned from the Publish( ) method have been set. So, if you use more than one handler for a given event, you need to use caution in defining and using the parameters for that event.
Also, if you raise ERROR or throw an error object from any one of the handlers for the ABL class event, any event handler that has not already run when the error is raised does not run. Therefore, if you want all handlers to run for an event, regardless of error conditions, you must resolve all conditions within each handler and allow the handler to return successfully.