with a publicly exposed collection any consumer can alter the
collection. plus it exposes the type of implementation. if you needed
to change the implementation (say a list to set or vice versa) that
could impact other areas of the system. if it were encapsulated it
would only happen in a single class. encapsulation would also solve
your null Municipality issue. you could encapsulate this logic into a
single place.
taking it one step father you could encapsulate the creation of a city
by declaring it within a municipality.
class Municipality
{
AddNewCity(string name)
{
if(citys.Exists(c=>c.Name == name)) return;
citys.Add(new City(name, this));
}
}
class City
{
pubic virtual string Name {get; private set;}
pubic virtual Municipality Municipality {get; private set;}
internal City(string name, Municipality municipality)
{
Name = name;
Municipality = municipality
}
}
it's a simple change but it has a big impact. you can begin to define
the rules directly into the domain objects. now if you want to create
a city.
using(var tx = session.BeginTransaction())
{
try
{
session.Get<Municipality>(1L).AddNewCity("New York");
tx.Commit();
}
catch
{
tx.Rollback();
throw;
}
}
yes, if you remove one of the relationships it becomes unidirectional.
On Nov 10, 4:24 pm, Kasper Nielsen <[email protected]> wrote:
> Thanks a lot for your answers Jason - quite a lot to take into
> consideration :-)
>
> But: Wouldn't it make sense to be able to create a new City and add it
> to a municipality like this:
>
> Municipality mun = Load(...);
> mun.Cities.Add(new City() { Name = "Cityname" });
> session.DoSomeSaveStuff();
>
> Or is it just me? I think the above would be quite intuitive.
>
> And it also makes me think: What if the relationship was only
> implemented on the Municipality class (that's an unidirectional
> mapping right?)
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