[GNC-dev] Python-Bindings: issue when C expects GList argument

[Matteo Lasagni]

Thank you, John!

I fixed it by adding the following into base-typemaps.i:

%typemap(in) GList * {
    $1 = NULL;
    /* Check if is a list */
    if (PyList_Check($input)) {
        int i;
        int size = PyList_Size($input);
        for (i = size-1; i >= 0; i--) {
            PyObject *o = PyList_GetItem($input, i);
            $1 = g_list_prepend($1, o);
        }
    } else {
        PyErr_SetString(PyExc_TypeError, "not a list");
        return NULL;
    }
}

I had overlooked the swig definition in engine.i, where there is a typemap
(in) for GList, but then it is cleared right afterwards...
I am not (yet) very familiar with swig :-)

I have also noticed that CreatePaymentLotSecs does not work out of the box,
as it expects **Transaction while only *Transaction is type mapped.

I will test these changes then I will figure out how to share them with the
developers.


Matteo


On Tue, 10 May 2022 at 02:32, John Ralls <jralls at ceridwen.us> wrote:

>
>
> > On May 9, 2022, at 2:17 PM, Matteo Lasagni <laser820 at gmail.com> wrote:
> >
> > Hi,
> > I am writing a python script to automatically associate a set of
> > invoices to a single transaction.
> > To this end, I am trying to use the function AutoApplyPaymentsWithLots
> > with no success:
> >
> >
> > lots = [lot1, lot2, lotn, ..]
> > owner.AutoApplyPaymentsWithLots(lots)
> >
> > This causes the following error:
> >
> > TypeError: in method 'gncOwnerAutoApplyPaymentsWithLots', argument 2 of
> > type 'GList *'
> >
> > I have tried different solutions from passing different types of python
> > objects, to updating the swig typemap and also to modifying the
> > auto-generated gnucash_core.c...nothing worked out so far.
> > I could write an additional c-wrapper, but I am sure there is a more
> > general solution.
>
> The fundamental problem is that there's only a Python out typemap for
> GList, that is one that converts from a GList* to a python list. Lacking an
> in typemap the gncOwner.AutoApplyPaymentsWithLots python wrapper expects an
> already constructed and Swig-wrapped GList*.
>
> Regards,
> John Ralls
>
>

-- 

-------------
Matteo Lasagni


*"You can't connect the dots looking forward,you can only connect them
looking backwards"* [Steve Jobs]