The OpenEdge Hive

Hello! In our application we need some classes to be created only once. I will implement these classes as singletons (with the help of the static keyword in 10.1.C)


METHOD PUBLIC STATIC CLASS CLSBETaskUserBase getInstance():
IF NOT VALID-OBJECT (clsBEModel) THEN
clsBEModel = NEW CLSBETaskUserBase().
RETURN CAST (clsBEModel, CLSBETaskUserBase).
END METHOD.


As I am not willing to implement the getInstance() method in every businessentity, I want to place a getInstance() in the superclass with an additionaly string-parameter, which will indicate the type of class to create, e.g.


METHOD PUBLIC STATIC CLASS CLSBusinessEntity getInstance (INPUT arg AS CHARACTER):
DEFINE VARIABLE cls AS Progress.Lang.Class NO-UNDO.
cls = PROGRESS.Lang.Class:GetClass(arg).
clsBEModel = CAST(cls, PROGRESS.lang.class:getclass(arg)).
RETURN clsBEModel.
END METHOD.

The call was thought to be like this:

DEFINE VARIABLE clsBE AS CLASS CLSBETaskPerson.
clsBE = CLSBusinessEntity:getInstance(
"CLSBETaskPerson").
.
.
.

*/

FYI:
CLSBusinessEntitiy is the superclass of CLSBETaskUserBase.

This code compiles fine, but at runtime a exception resp. an error is raised telling me about an illegal cast-operation.

How can I created an object dynamically at runtime like I can do this in Java? Does anybody know? I think in my code...there must be an error.

First I tried to use an interface to force every businessentity to override the method getInstance(), but I cannot place a static method in an interface.

The second attempt was to place the getInstance() in the superclass - the result is an illegal cast (see codesniplet above). Of course it can be that the second code is wrong - if anyone can tell me how I can make it - thank you very much.

Greetings
Harry