How can I call a swig python function when a parameter is using typedef int

Question

I have a C++ API I'm trying to wrap in Python.There is a function Foo(TAPIINT32 &iResult) with typedef int TAPIINT32 in header file.When I use: a=0 mymodule.Foo(a) in python to call it,I get an error as "TypeError: in method 'Foo', argument 1 of type 'TAPIINT32 &'".Is anybody could help with this?Many thanks!

Mark Tolonen · Accepted Answer · 2017-10-09 21:49:27Z

1

SWIG needs to be told when parameters are outputs and has pre-existing typemaps to help. Here's an example:

api.h

typedef int TAPIINT32;
void Foo(TAPIINT32& iResult);

api.cpp

#include "api.h"

void Foo(TAPIINT32& iResult)
{
    iResult = 5;
}

api.i

%module api

%{
#include "api.h"
%}

%include <windows.i>
%apply int* OUTPUT {TAPIINT32t&};
%include "api.h"

The %apply command tells SWIG to apply an existing typemap to the indicated type. In this case, the pre-existing int* OUTPUT typemap is applied to all TAPIINT32& parameters. Note that the OUTPUT typemap suppresses the need for passing a parameter, and returns it as an additional return value instead.

Output:

>>> import api
>>> api.Foo()
5

edited Oct 9, 2017 at 21:49

answered Oct 9, 2017 at 18:04

Mark Tolonen

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1 Comment

George Over a year ago

Thank you very much.It solved this problem perfectly.

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