[news.eclipse.modeling.gmf] Re: Shortcut for 1:1:n containment reference

[c.muth@xxxxxx (Christian Muth)]

Hello Alex,


first, let me thank you for your valuable help.

> > model so that i can ask A for instances of C. (containment, derived,
> > transient references from A->C) - Remember: A->B is 1:1 containment
> This is a right solution for now with only addition â?? this reference 
should 
> not be containment and GMF should allow you to specify non-containment 
reference 
> as containment one in ChildReference (you should be able to igronre warning 
> on map->gen transformation and generate code then).
I'll soon have a look at the GMF sources to enable selection of 
non-containment references. As I can't imagine any other expedient 
constraint (than being containment) on the selectable references, I'll 
hand it over to the toolsmith to care for the sanity of his/her selection.

> > Might it eventually be possible to extend GMF to support this? If so,
> I think, generic support of this situation is rather complex, so I doubt 
> support this kind of  â??complex diagram structure modellingâ?? will be 
implemented 
> in GMF in near future. As you correctly found there is a workaround for this 
> problem â?? you can use EMFâ??s derived features + java to implement all the 
> logic there so for GMF this will be still a parent domain model element 
(indirectly) 
> containing child one.. 
> Nevertheless for now you can try modifying GMF templates (using custom 
templates 
> for this diagram editor generation) to handle this situation at least to 
> some extend. Once youâ??ll find a solution you can simply raise a bugzilla 
> request with appropriate patch attached to contribute this functionality 
> into the project.
Ok, so I'll rather create a plugin extending EMF to be able to create 
these "shortcut" references semi-automatically. I agree with you this 
being the better way of solving my issues.

> First of all you have to modify templates generating CreateCommand to 
properly 
> create intermediate element + properly assign child element to the chain 
> of containment feature. In this case an entry point will be 
xpt/diagram/commands/CreateNodeCommand.xpt 
> template.
The child element assignment is no problem at all, I use Feature Seq 
Initializers for that which work well.

> Then youâ??ll probably face some problems with update logic. This part will 
> not be so simple (update is quite compex place in GMF) and in this case you 
> have to start with xpt/diagram/updater/DiagramUpdater.xpt template. 
So far i didn't see any problems with that. Since I delegate all accessor 
methods completely to the target class (from A->B->C): 
A.getB().getC().getSomeCollection().add(...), C's accessor methods shold 
fire notifications properly, do they?

> I can not remember any other templates to be involved into this task, so 
> good luck and ping me if you get any more questions.
Thanks a lot, Alex. BTW: Working with GMF is great fun!


Cheers

Christian