[news.eclipse.modeling.m2m] Re: How to work with circular references?

[max.bureck@xxxxxxxxxxxxxxx (Max Bureck)]

Ok, I could write one B to Y,Z with the precondition, that the Z does not 
exists and one B to Y rule with the precondition that Z does exists and 
set the reference from B to the existing Z in the body of the rule. This 
is a bit lengthy, because the B to Y rule does a lot. Maybe I can use 
abstract rules and inheritance to eliminate the duplicate parts of the 
rules.

> Hello,

> I'm having some trouble with circular references lately. How do I cope 
> with the situation, that two output elements have references to the same 
> third element?
> In one case it was like that:

> Input model:
> A
> |-B
> |-B

> Mappings:
> A to X
> B to Y,Z

> Output model:
> X
> |-Y--Z
> |-Y-/

> So that both Y-model elements have a reference to the same Z.
> Is there declarative way to express that?
> My only idea is to create a helper-method, which is called in Mapping B to 
> Y that checks if Z already exists. If Z exists, it returns it, if not, it 
> calls a lazy rule creating Z. Is this the way to go, or is there a better 
> way?