I've found the answer....I must put Alois's book in the car - or is there a PDF download?

The calling object is always passed as Parameter[0]

Nick

Thanks

Nick

Downloading now......

Assuming a model like

Product 0..*----0..1 Category

Category "0..1 ParentCategory" ----- "0..* ChildCategory" Category

If you want to find all products that belong to all child categories of a parent category you can do Ocl like:

Product.allInstances->select( p | p.Category.IsParentInTree(p.Category, Category.objectFromExternalId('1!1'), 'ParentCategory')

Any ideas on how to make this more efficient welcome, however, the Ocl must be based from the Product class.

Hope this is useful to someone....

Nick

procedure OclParentInTree.Evaluate(Parameters: IOclOperationParameters);
var
  ObjectToFind: IObject;
  CallingObject: IObject;
  AssociationName: string;
  CallingObjectElement: IElement;
  ObjectToFindElement: IElement;
  IsInTree: Boolean;
begin
  CallingObjectElement := Parameters.Values[1].Element;
  ObjectToFindElement := Parameters.Values[2].Element;

  CallingObject := CallingObjectElement as IObject;

   ObjectToFind := ObjectToFindElement as IObject;

  AssociationName := Support.GetAsString(Parameters.Values[3]);

  IsInTree := RecurseTree(CallingObject, AssociationName, ObjectToFind);

  Support.MakeNewBoolean(Parameters.Result, IsInTree );
end;

procedure OclParentInTree.Init;
var
  OclParameters: array of IOclType;
begin
  SetLength(OclParameters, 4);
  OclParameters[0] := Support.ObjectType;
  OclParameters[1] := Support.ObjectType;
  OclParameters[2] := Support.ObjectType;
  OclParameters[3] := Support.StringType;
  InternalInit('IsParentInTree', OclParameters, Support.BooleanType);
end;

function OclParentInTree.RecurseTree(CallingObject: IObject;
  AssociationName: string; ObjectToFind: Iobject): Boolean;
var
  ObjectToFindId, CallingObjectId: string;
begin
  ObjectToFindId := support.ExternalIdService.IdForObject(ObjectToFind);
  CallingObjectid := support.ExternalIdService.IdForObject(CallingObject);

  if (CallingObjectId = ObjectToFindId) then
    Result := True
  else
  begin
    try
      Result := RecurseTree(CallingObject.Properties.Item[AssociationName] as IObject, AssociationName, ObjectToFind);
    except
      Result := False;
    end;
  end;
end;

I'm building a dynamic search page with multiple search fields so I wanted to be able to start all my Ocl

Product.allInstances->select.....->select(.....->select(....

> My alternative suggestion would be to define a derived association "allChildren" (0..*) from category to category that is defined recursively:

I think I might use this, but I may do it with a custom Ocl function so I can call

Category.AllChildObjects('AssociationName').Products

This way I'm not relying on it being coded in the model.

If my user selects a category and another hierarchical association my Ocl could then be

Category.AllChildObjects('AssociationName').Products->Intersection(OtherHierarchicalClass.AllChildObjects('OtherAssociationName').Products)->select(Name.SqlLike(''''))

I hadn't noticed the "Intersection" function until now, so I couldn't see how to do the above without starting at the Product class and having chained selects.

> This way you don't have to load products that you don't want in the end result.

This would be much better.

Would there be any (much) performance difference between the Derived Association method and the Ocl function method?

Thanks for your help

Nick