Re: (Real)DictConnection is not compatible with the adaptation mechanism

On Thu, Jan 22, 2009 at 2:20 AM, Lawrence Oluyede <[email protected]> wrote:
> I tried to register an adapter for a SQL type following the examples
> and the documentation and it all worked fine.
> My problem manifested itself when I tried to integrate the code with
> the real application which uses (Real)DictConnection.
>
> When I register the new type with:
>
> psycopg2.extensions.register_type(NEWTYPE, conn)
>
> it breaks with the following error:
>
> TypeError: argument 2 must be a connection, cursor or None
>
> which is located in psycopgmodule.c in function psyco_register_type.
>
> It seems that it checks for "cursorType" and "connectionType"
> preventing inherited objects to work with the adaptation mechanism:
>
> psyco_register_type(PyObject *self, PyObject *args)
> {
>   [...]
>
>    if (obj != NULL) {
>        if (obj->ob_type == &cursorType) {
>            _psyco_register_type_set(&(((cursorObject*)obj)->string_types),
> type);
>        }
>        else if (obj->ob_type == &connectionType) {
>            typecast_add(type, ((connectionObject*)obj)->string_types, 0);
>        }
>        else {
>            PyErr_SetString(PyExc_TypeError,
>                "argument 2 must be a connection, cursor or None");
>            return NULL;
>        }
>    }

You could try replacing the type checks with e.g.

    PyObject_TypeCheck(obj, &cursorType)

That should handle the subclassed connection correctly.  If you try
this, please tell us whether it is successful or not so we can fix it
in future versions.

James.