NHibernate / Fluent - Mapping multiple objects to single lookup table
- by Al
Hi all
I am struggling a little in getting my mapping right.
What I have is a single self joined table of look up values of certain types. Each lookup can have a parent, which can be of a different type.
For simplicities sake lets take the Country and State example.
So the lookup table would look like this:
Lookups
Id
Key
Value
LookupType
ParentId - self joining to Id
base class
public class Lookup : BaseEntity
{
public Lookup() {}
public Lookup(string key, string value)
{
Key = key;
Value = value;
}
public virtual Lookup Parent { get; set; }
[DomainSignature]
[NotNullNotEmpty]
public virtual LookupType LookupType { get; set; }
[NotNullNotEmpty]
public virtual string Key { get; set; }
[NotNullNotEmpty]
public virtual string Value { get; set; }
}
The lookup map
public class LookupMap : IAutoMappingOverride<DBLookup>
{
public void Override(AutoMapping<Lookup> map)
{
map.Table("Lookups");
map.References(x => x.Parent, "ParentId").ForeignKey("Id");
map.DiscriminateSubClassesOnColumn<string>("LookupType").CustomType(typeof(LookupType));
}
}
BASE SubClass map for subclasses
public class BaseLookupMap : SubclassMap where T : DBLookup
{
protected BaseLookupMap()
{
}
protected BaseLookupMap(LookupType lookupType)
{
DiscriminatorValue(lookupType);
Table("Lookups");
}
}
Example subclass map
public class StateMap : BaseLookupMap<State>
{
protected StateMap() : base(LookupType.State) { }
}
Now I've almost got my mappings set, however the mapping is still expecting a table-per-class setup, so is expecting a 'State' table to exist with a reference to the states Id in the Lookup table.
I hope this makes sense.
This doesn't seem like an uncommon approach when wanting to keep lookup-type values configurable.
Thanks in advance.
Al
