Home → Help and guidance →

Mapping property using backing field with different type.

Niklas Källander

28 Jul, 2010 10:06 AM via web

Admin Functions

• Edit
• Remove

Hi,

It seems that using fluent nhibernate's current access strategy syntax breaks the mapping when using different types on the property and the backing field if the property has a non-supported type. However, it works fine using the Reveal.Member<Source, Return>() strategy, but that requires magic strings which I'm not very fond off.

The code I want to map looks like:

private IList<MyType> m_MyTypes;
public virtual MyList<MyType> MyTypes 
{ 
    get { return MyList.From(m_MyTypes); } 
}

The mapping code I would want looks like:

HasMany(x => x.MyTypes)
    .Access.PascalCaseField(Prefix.mUnderscore);

The mapping I am forced to use due to this bug looks like:

HasMany<MyType>(x => Reveal.Member<MyParentType, IList<MyType>>("m_MyTypes"));

Which not only introduces magic strings but also forces me to enter a lot of type parameters.

I've also tried using this code, which I could live with:

HasMany(x => x.MyTypes)
    .Access.PascalCaseField(Prefix.mUnderscore)
    .CollectionType<IList<MyType>>();

But it gives me this error:
Custom type does not implement UserCollectionType: System.Collections.Generic.IList`1[[MyType]].

Is this something you've already recognized(?) and if so, do you have any plans to fix it in a coming release? :)

Besides this small limitation Fluent NHibernate is truly awesome!

Best regards,
Niklas Källander

1. 2 Posted by Niklas Källander on 28 Jul, 2010 11:51 AM

   

   Hi again,

   Seems that I was way wrong about this working ( thought I got it to work though ):

   HasMany<MyType>(x => Reveal.Member<MyParentType, IList<MyType>>("m_MyTypes"));
   

   But even if I use it correctly e.g:

   HasMany<MyType>(Reveal.Member<MyParentType>("m_MyTypes"));
   

   It does not work, it can't find the "property" named "m_MyTypes", however, the documentation for Reveal.Member says "Reveals a hidden property or field for use instead of expressions".

   Best regards,
   Niklas Källander

   Admin Functions

   • Edit
   • Split
   • Remove

2. 3 Posted by cremor on 29 Jul, 2010 06:19 AM

   

   I don't know about your main problem, but for your workaround you need to specify field access:

   Reveal.Member<T>("field")).Access.Field()
   

   Admin Functions

   • Edit
   • Split
   • Remove

3. 4 Posted by Niklas Källander on 29 Jul, 2010 09:00 AM

   

   Hi Cremor,

   Thanks for the response, never thought of adding that myself since the documentation said the Revel.Member could handle fields as well ( thought it looked for both )! Thank you! :)

   The main issue, however, is still not solved, but I managed to get rid of the magic strings by inheriting ClassMap<> adding more functionality to my maps that are based on my own conventions. :)

   Best regards,
   Niklas Källander

   Admin Functions

   • Edit
   • Split
   • Remove