[fpc-pascal] Problem accessing Class Method with abstraction

[Andrew Hall]

The reason you cannot call VerifyID's from coGeneric is that the compiler sees coGeneric as a TPersistentClass which does not implement the VerifyIDs method.   The following changes will give you the desired result...

type 
  TCoreObjectClass = class of TCoreObject;

If (coGeneric<>nil) and coGeneric.InheritsFrom(TCoreObject) then
  TCoreObjectClass(coGeneric).VerifyIDs(Module);

Regards Andrew.


On 17 Oct 10, at 06:38 , Andrew Brunner wrote:

> procedure VerifyIDs(Var Module:TDBMSModule);
> var
>  iLcv:integer;
>  ItemP:PCoreObjectItem;
>  coGeneric:TPersistentClass;
>  coItem:TCoreObject;
> begin
>  for iLcv:=0 to High(CoreObjectItems) do begin
>    ItemP:=CoreObjectItems[iLcv];
>    coGeneric:=GetClass(ItemP^.ClassName);
>    if (coGeneric<>nil) and coGeneric.InheritsFrom(TCoreObject) then begin
>      coItem:=coGeneric.Create as TCoreObject;
>      Try
>        coItem.VerifyIDs(Module);
>      finally
>        FreeAndNil(coItem);
>      end;
>    end;
>  end;
> end;
> 
> This code works as expected but why do I need to create an instance of
> the object if I just want to reference it's class procedure of
> VerifyIDs?
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