A quoted string or character expression representing the name of a callback. The callback-name is not case-sensitive.
routine-name
A quoted string or character expression representing the name of a method or an internal procedure that resides within routine-context.
routine-context
An object reference for a class instance or a handle to a persistent procedure that contains the method or internal procedure specified by routine-name. If not specified, and the routine is executed within a procedure, THIS-PROCEDURE is used as the routine context. If not specified, and the routine is executed within a class instance, THIS-OBJECT is used as the routine context.
If callback-name is not a valid callback, or routine-context is not a valid object reference or handle, this method returns FALSE; otherwise, it returns TRUE. If the SET-CALLBACK( ) method is specified but cannot be invoked, or it fails, no method or procedure is executed as part of the callback event.
Notes
If routine-name represents a class method that is associated with an ABL event as a callback, and the method is overridden in a derived class, the overridden method is run when the callback is invoked.
When used with a class instance, the SET-CALLBACK( ) method creates an internal reference to the instance. As a result, the instance can never be garbage collected.
If routine-name represents a class method that is associated with an ABL event as a callback, and the method is overridden in a derived class, the overridden method is run when the callback is invoked.