[fpc-devel] Parameters must match exactly?

[Michael Van Canneyt]

On Mon, 17 May 2010, Graeme Geldenhuys wrote:

> Hi,
>
> Sorry, I'm still battling with this. My original code looked as follows:
>
> procedure TfpgApplicationBase.CreateForm(AFormClass: TComponentClass; out
> AForm: TfpgWindowBase);
> begin
>  try
>    AForm := TfpgWindowBase(AFormClass.Create(self));
>    if FMainForm = nil then
>      FMainForm := AForm;
>  except
>    AForm := nil;
>    raise;
>  end;
> end;
>
>
> I then used that method as follows:
>
> var
>  BulkDiscountListForm: TBulkInvoiceRateListForm;
>
> function DisplayMyForm: boolean:
> begin
>  fpgApplication.CreateForm(TBulkInvoiceRateListForm,
>     BulkDiscountListForm);
>  try
>    Result := BulkDiscountListForm.ShowModal = mrOK;
>    if Result then
>      // save data
>  finally
>    BulkDiscountListForm.Free;
>  end;
>  ...
> end;
>
>
> This doesn't work with FPC 2.5.1.  I then removed the 'out' parameter type
> and my code compiled, but now it gives the following compiler warning all
> over the place for each form I create.

And correctly so, because you need the OUT: you are modifying the pointer
and need to pass back the modified pointer to the caller.

Michael.