Re: Unable to access referenced parameter in Python callback

A few tweaks and below works for me:

%module(directors="1", allprotected="1") example
%feature("director") Base;

%inline %{
enum PropertyType{PT_REAL, PT_STRING};
class Property
{
    public:
        PropertyType GetType() const;
        int GetSize() const;
};

class Base
{
    public:
        virtual bool Start(const Property& config) = 0; // PASSED AS
REFERENCE

};

void callup(Base& b, Property& p) {
  b.Start(p);
}
%}
%{
  PropertyType Property::GetType() const { return PT_REAL; }
  int Property::GetSize() const { return 1; }
%}


from example import *

class PyClient(Base):
    def Start(self, config):
        config_size = config.GetSize()
        config_type = config.GetType()
        print("Got {} {}".format(config_size, config_type))
        return True


prop = Property()
pc = PyClient()
callup(pc, prop)

William


On Fri, 17 Sept 2021 at 13:49, Ben van Basten via Swig-user <
[email protected]> wrote:

> Hello!
>
>
>
> In SWIG, I've got a wrapped C++ base class that is inherited in Python.
> The C++ side invokes callbacks on the Python derived class, which works
> fine. Unfortunately, one of the parameters of the callback is passed as
> reference. Accessing this reference yields:
>
>
>
> Fatal unhandled exception: SWIG director method error. Error detected when
> calling 'Base.Start'
>
>
>
> test.i
>
>
>
> %module(directors="1", allprotected="1") test
>
> %feature("director") Base;
>
>
>
> class Base
>
> {
>
>     public:
>
>         virtual bool Start(const Property& config) = 0; // PASSED AS
> REFERENCE
>
>
>
> };
>
>
>
> enum PropertyType{PT_REAL, PT_STRING};
>
> class Property
>
> {
>
>     public:
>
>         PropertyType GetType() const;
>
>         int GetSize() const;
>
> };
>
>
>
> In Python, Start is correctly callback/invoked. Unfortunately, invoking
> GetType() or GetSize() yields the error above. Invoking functions of
> parameters passed as pointer is going fine.
>
>
>
> import test
>
>
>
> class PyClient(test.Base):
>
>     def Start(self, config):
>
>         config_size = config.GetSize() // YIELDS ERROR
>
>         config_type = config.GetType() // YIELDS ERROR
>
>         return True
>
>
>
> I guess I need to convert the parameter Property from a reference to a
> pointer, but it is unclear to me how this works in SWIG.
>
>
>
> I’m using VS2017. SWIG 4.02, Python 3.7 64bit
>
>
>
> Any help would be really appreciated.
>
>
>
> Ben
>
>
> _______________________________________________
> Swig-user mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/swig-user
>

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