Shared aggregations

[frankk]

I have a hierarchy of classes starting from, say, A. Below A are two subclasses, B and C. B is an aggegation of D, E and F. C is also an aggregation of D, E and F. Is there a clean way to show that B and C both aggregate D, E and F, i.e., without duplicating D, E and F explicitly?

(P.S.: How do I upload/insert/attach diagrams?)

[thomas.kilian]

I don't see the problem here. You will simply have association links with aggregates from D, E and F to B and C.

You can attach pictures to any web location (there are providers to store pictures; there's a thread here which links to one pre-set provider but I forgot where).
Use Neil's link below. That's working pretty neat.

[KP]

You can attach pictures to any web location (there are providers to store pictures; there's a thread here which links to one pre-set provider but I forgot where).

I use http://www.imageshack.us/. I have no idea if it's better or worse than any other image hosting site, but it's free and you can link to pictures directly.

[Torsten Binias]

Hi,

why doesn't A then aggregate D, E and F?

    +-----+        +-----+
     !     !<>------!  D  !
     !     !        +-----+
     !     !        
     !     !        +-----+
     !  A  !<>------!  E  !
     !     !        +-----+
     !     !
     !     !        +-----+
     !     !<>------!  F  !
     +-----+        +-----+
        ^
       / \
       ---
        !
        !
   +----+-----+
   !          !
+-----+   +-----+
!  B  !   !  C  !
+-----+   +-----+


Best regards,
Torsten

[«Midnight»]

Sorry Torsten, but I'm not sure I get the question.

Do you mean "why don't B and C aggregate D, E, and F?"

If so, could it be a visibility setting? Perhaps you have the appropriate attributes of A set to private instead of protected. Or perhaps you need to explicitly define the attributes - I think there's an ongoing thread about this case.

David

[Frank Horn]

David,

I think Torsten simply wanted to ask why frankk wants to have the three associations in both derived classes B and C, and not define them on the base class A.

A reason for this could be that other classes without these associations are to inherit from A, and a language without multiple inheritance capability is being used.

This does not mean that I understand the original problem.

Frank

[«Midnight»]

Yup,

That's about where I came in...

David

[KP]

Torsten's post may have been worded as a question, but I think it was intended as the answer (correct, IMO) to the original question "Is there a clean way...?"

[Torsten Binias]

Hello,

yes, I tried to give an answer to the original question. Didn't mean to confuse everbody... :-)

A reason for this could be that other classes without these associations are to inherit from A, and a language without multiple inheritance capability is being used.

If that is the case then A can have a superclass from which those other classes can be derived.

Best regards,
Torsten