Kbase P21216: The 'One Session one WAIT-FOR' golden rule
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
11/1/2007 |
|
Status: Verified
GOAL:
What is the "One Session one WAIT-FOR" golden rule?
GOAL:
Multiple windows with multiple WAIT-FOR statements
FACT(s) (Environment):
Progress/OpenEdge Versions
All Supported Operating Systems
FIX:
Many problems can occur when managing multiple windows with multiple WAIT-FOR statements in one session.
The purpose of this rule is to not have to worry about nesting correctly multiple WAIT-FOR's. Multiple WAIT-FOR are necessary only when there is a need to force a sequential RUN, by stopping the flow of the Program(s).
Easiest to apply this rule is to run children window procedures persistently as shown bellow:
/* in ParentWindow.w*/
RUN ChildWindow.w PERSISTENT.
In ChildWindow.w, see the importance of the following line that come by default in the main block of the window template:
IF NOT THIS-PROCEDURE:PERSISTENT THEN
WAIT-FOR CLOSE OF THIS-PROCEDURE.
Since the ChildWindow.w procedure is running persistently, the WAIT-FOR will not occur and the flow of the program will go back to parentWindow.w (after RUN ChildWindow.w PERSISTENT.)
Indeed, the second window does not require a WAIT-FOR to be alive and make its contained widgets and itself sensitive. The default window template works in such a way that the persistent procedure will be deleted by the disable_UI procedure when the WINDOW-CLOSE event is fired for the window widget.