[news.eclipse.tools.emf] Re: containment co-existing with references for

[Frank Budinsky <frankb@xxxxxxxxxx>]

Nikolaj,

The only way you can have a feature that returns a mixture of contained and
non-contained objects is by making it volatile.

For example, you could make the "see" property of class A volatile and then
implement the getSee() method to return all of the contained C's (you'd need
another feature in class A for them) merged with the C's that are under the
B's returned by getFoo().

Frank.


Nikolaj Berntsen wrote:

> Hi,
>
> Is it possible to have a class, B, have a property 'prop' of type C,
> that is either contained or referenced (contained in  another class A)?
>
> Phrased differently: Is it necessary to have one property for references
> and another for containment?
>
> For example:
>
> Class A can contain class B and C. Class B can contain class C. Can
> class B also have the possibility of referencing an instance of Class C
> contained in class A and contain another instance of Class C.
>
> In some kind of pseudo XML notation:
>
> <A>
>   <B prop="//@A//@C.1">
>    <C/>
>   </B>
>   <C/>
> </A>
>
> Written in java interfaces it would be something like the following code
> - with the unclear points marked XXX and YYY:
>
> /** @model */
> interface A {
>    /** @model containment="true" */
>    B getFoo();
>
>    /** @model containment="true" XXX */
>    C getSee()
> }
>
> /** @model */
> interface B {
>    /** @model containment=true YYY */
>    C getProp();
> }
>
> Perhaps it is something to do with opposite="..."? or using both
> container="..." and contaiment="..."?
>
> I must admit I haven't experimented much with it, but reading the
> documentation does not make the answer clear to me.
>
> I think it would be a nice thing to be able to do. Imagine class C
> being, say, Image, and class B being Screen. Then some images would be
> used on different Screens and some would only belong to a single screen.
> It would be nice to be able to see that from the tree structure. Class A
> could then be the container of screens.
>
> Thanks in advance,
> /\/ikolaj