> So, I'm back with my initial problem, except I'm free to design the db
> schema as I see fit.
> But even with _no_ constraint watsoever, I can't seem to find a correct
way
> to map my classes to my DB.
>
> The scenario is simple, and probably very common too (still the same
> scenario as my initial post) :
> We've got Clients. Clients can be businesses or customers.
> So in terms of classes, we have Client, Contact and Company.
> A Contact has a property Client (may be null because not all Contacts are
> clients). Same for Company.
> And a Client has two properties, Contact and Company, but only one of them
> is non null.
I find it hard to follow: a client can be a business or a customer,
yet you say you have client, contact and company. Where's customer?
Also you shouldn't think in properties, but in relationships. FK
side depends on PK side, and only 1 PK side. What you want is to switch
between PK sides for a given FK side, that's nonsense, since the FK side's
fields (for mapping, the FK fields in the table you map in the mapping
files) are derived from the PK fields they refer to. That's what it means:
Customer 1:n Order -> Order gets the PK field of Customer as FK field. You
seem to want to switch between PK sides, which is incorrect.
However, I fail to see why you want this. You don't think in
entities and their relationships but in code and how to cram that into some
tables. That's the wrong way to look at things: try first to determine which
entities you have (I assume: Client, Company (subtype of Client) and
Customer (subtype of Client), and Contact) and how they relate to eachother,
THEN try to create a model from that in the DB, preferably by using T.A.
Halpin/Nijssen's approved system to project an abstract entity model with
inheritance onto a relational model, e.g. what's been used in ORM/NIAM. This
is pretty straight forward, you have to make a decision whether you want to
create 1 target (table) for an inheritance hierarchy or 1 table for each
entity in the inheritance hierarchy but that's about it. The main problem is
which entities there are, and how they relate to eachother, as you don't
seem to have that figured out yet.
FB
> We could model that with an abstract class Client, and two contrete
classes,
> BusinessClient that has a non null Company property and a CustomerClient
> that has a non null Contact property.
>
>
> The natural (for me) db schema doesn't work (cf earlier post).
> So I'm trying to have my one-to-one mappings on the primary key, that is
if
> a Client is b2c, then the Client PK is the PK of the Contact, and if a
> Client is b2b, the Client PK is the PK of the Customer.
>
> But that doesn't really work either because nHibernate Id generator
> "foreign" only accepts a single entity has a foreign key source.
>
> And Creating a class hierarchy doesn't work eigher because the generator
> must apparently be set at the root class.
>
> So I welcome any advice, because I'm somewhat stumped: my domain model is
> simple, yet I can't seem to find a good and simple way to map it to a
> storage model.
>
>
> Thanks
>
> Blaise
>
>
>
> On Jul 26, 2:49 pm, Fabio Maulo <[email protected]> wrote:
> > aaahhh you never said you are using a Eliot Ness DB.
> >
> > I'll check what happen with your Eliot Ness.
> >
> >
> >
> >
> >
>
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