Return values from ancestor scripts

If you want to perform some processing in an event in a descendent object, but that processing depends on the return value of the ancestor event script, you can use a local variable called AncestorReturnValue that is automatically declared and assigned the return value of the ancestor event.

The first time the compiler encounters a CALL statement that calls the ancestor event of a script, the compiler implicitly generates code that declares the AncestorReturnValue variable and assigns to it the return value of the ancestor event.

The datatype of the AncestorReturnValue variable is always the same as the datatype defined for the return value of the event. The arguments passed to the call come from the arguments that are passed to the event in the descendent object.

Extending event scripts

The AncestorReturnValue variable is always available in extended event scripts. When you extend an event script, PowerBuilder generates the following syntax and inserts it at the beginning of the event script:

CALL SUPER::event_name

You see the statement only if you export the syntax of the object.

Overriding event scripts

The AncestorReturnValue variable is available only when you override an event script after you call the ancestor event using the CALL syntax explicitly:

CALL SUPER::event_name

CALL ancestor_name::event_name

The compiler does not differentiate between the keyword SUPER and the name of the ancestor. The keyword is replaced with the name of the ancestor before the script is compiled.

The AncestorReturnValue variable is declared and a value assigned only when you use the CALL event syntax. It is not declared if you use the new event syntax:

ancestor_name::EVENT event_name ( )

Example

You can put code like the following in an extended event script:

IF AncestorReturnValue = 1 THEN
  // execute some code
ELSE
  // execute some other code
END IF

You can use the same code in a script that overrides its ancestor event script, but you must insert a CALL statement before you use the AncestorReturnValue variable:

// execute code that does some preliminary processing
CALL SUPER::ue_myevent
IF AncestorReturnValue = 1 THEN
…