Master/Detail

BIZ TMS Aurelius
1
I have a master/Detail relationship mapped as follows:

  [Entity]
  [Table('TBLREZEPT')]
  [Id('FREZEPTID', TIdGenerator.None)]
  TTBLREZEPT = class
  private
    [Column('REZEPTID', [TColumnProp.Required, TColumnProp.NoUpdate])]
    FREZEPTID: Integer;
   
    [ManyValuedAssociation([TAssociationProp.Lazy, TAssociationProp.Required], CascadeTypeAll , 'FREZEPTID')]
    FTBLREZEPTZUTATList: Proxy<TList<TTBLREZEPTZUTAT>>;
  public

and 

  [Entity]
  [Table('TBLREZEPTZUTAT')]
  [Id('FREZEPTID', TIdGenerator.None)]
  [Id('FREZEPTPOSID', TIdGenerator.None)]
  TTBLREZEPTZUTAT = class
  private
    [Column('REZEPTPOSID', [TColumnProp.Required, TColumnProp.NoUpdate])]
    FREZEPTPOSID: Integer;
   
    [Association([TAssociationProp.Lazy, TAssociationProp.Required], CascadeTypeAll - [TCascadeType.Remove])]
    [JoinColumn('REZEPTID', [TColumnProp.Required], 'REZEPTID')]
    FREZEPTID: Proxy<TTBLREZEPT>;

This is a legacy DB, so I provide the IDs myself Prior to inserting the records.

Adding is no Problem:
SAVE the REZEPT
add and save each ZUTAT:
                      Zutat := TTblrezeptzutat.Create;
                      Zutat.REZEPTPOSID := uc.GetNextID('tblrezeptzutat.rezeptposid');
                      mgrManager.Save(Zutat);
                      Rezept.TBLREZEPTZUTATList.Add(Zutat);


However, when I want to update the REZEPT, i first want to delete all ZUTAT:

          for Zutat in Rezept.TBLREZEPTZUTATList do begin
            mgrManager.Remove(Zutat);
          end;

The DELETE Statements are created and executed.

However, adding fails:
                      Zutat := TTblrezeptzutat.Create;
                      Zutat.REZEPTPOSID := uc.GetNextID('tblrezeptzutat.rezeptposid');
                      mgrManager.Save(Zutat); < --------------------- ERROR

Im Projekt RezeptSchnittstelle.exe ist eine Exception der Klasse EMappingNotFound mit der Meldung 'Cannot find mapping [Id] on class "nil".' aufgetreten.

This is weird, because without the removing, this works ok.

Any idea?
2

When you remove the objects, make sure to also remove the Zutat objects from the parent list. Otherwise the list will reference destroyed objects.

Alternatively, you can use

mgrManager.DeferDestruction := True;

to prevent removed objects from being destroyed until the object manager itself is destroyed.
3
>make sure to also remove the Zutat objects from the parent list.

This is the list of the parent: Rezept.TBLREZEPTZUTATList.
Do you mean remove, removeitem or delete?
4

Something like this:


          for Zutat in Rezept.TBLREZEPTZUTATList do begin
            Rezept.TBLREZEPTZUTATList.Remove(Zutat);
            mgrManager.Remove(Zutat);
          end;
5
Ok, thanks for that. I'll give it a try.

But I am unsure - why does this not work?
  for Zutat in Rezept.TBLREZEPTZUTATList do begin
            Rezept.TBLREZEPTZUTATList.Remove(Zutat);
          end;
mgrManager.Flush(Rezept);

6

Because it destroys the Zutat objects.

Then you can Flush(Rezept) but the Rezept object holds a list of the destroyed Zutat objects, which are inspected by Flush. When Flush tries to examine such destroyed objects, the AV is raised.
7

I see. Tx!