Dawid,
"One-to-many", "many-to-one", "one-to-one" and "one-to-many" refer to
relations between *entities*, not values. While NHibernate perfectly
supports collections of values and components, which are not entities, it
just does not call them "one-to-many", etc.
RP
On Friday, May 9, 2014 5:27:07 AM UTC+1, Dawid Ciecierski wrote:
>
> Hello,
>
> Let me say upfront that databases are not my area of expertise, so I may
> be saying something that is obviously wrong at first glance. (Apologies for
> wasting your time if this will turn out to be the case.) Secondly, this
> behaviour seems to be related to development a little more than users, thus
> posting here.
>
>
> *The Problem*
> SimpleModelInspector does not recognise collections of simple values
> (example below) as one-to-many, while in my view such dependent collections
> should automatically be marked as such (as well as inverse). At first I
> thought that this was a glitch and aimed to write a test that would
> demonstrate it; however, to my surprise there are already tests proving *the
> opposite* behaviour!
>
> The tests in question are WhenCollectionOfComponentsThenNoMatch and
> WhenCollectionOfElementsThenNoMatch inside OneToManyTests. To my
> (untrained) eye it seems they should be demonstrating that a collection of
> components and a collection of elements *should* in fact be marked as
> one-to-many (which it is currently not).
>
>
> *Why?*
> The particular use case in case you're wondering: having cascade-on-delete
> enabled on collections inside auto-mapped classes:
>
> public MyClass
> {
> public IList<string> Tags { get; set; }
> }
>
> public class MyModelMapper : ModelMapper
> {
> public MyModelMapper() : this(new SimpleModelInspector())
> {
> }
>
> public MyModelMapper(IModelInspector modelInspector) : base(modelInspector)
> {
> BeforeMapList += CascadeDeleteForChildCollections;
> }
>
> private void CascadeDeleteForChildCollections(
> IModelInspector inspector,
> PropertyPath member,
> ICollectionPropertiesMapper customizer)
> {
> if (inspector.IsOneToMany(member.LocalMember))
> {
> customizer.Inverse(true):
> customizer.Key(k => k.OnDelete(OnDeleteAction.Cascade));
> }
> }
> }
>
> (I know it is not always the best+safest idea to casdade, but in this case
> these are some utility tables, and not part of the core business domain.)
>
> Please do let me know if I'm wrong and this in fact is not a classic
> example of a one-to-many relationship, or if there perhaps exists another
> way to detect such collections with a model inspector and/or have them
> auto-SQL-cascade their deletes.
>
> Best regards,
> Dawid Ciecierski
>
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