[C++-sig] How to correctly expose back shared_ptr-ed Python object to C++

[Renato Araujo]

Hi Nodir,


I saw a problem in your exemple. But I did not know if is this your
problem, but try call the base constructor in your "PyTestPlugin"
constructor, like that:

> class PyTestPlugin(IBasePlugins):
>      def __init__(self):
            IBasePlugins.__init__(self) <<<<<<<<<<<<<<< here this need
be called explicitly
>          self.handle_type = 2
>      def canHandle(self, type):
>          return type == handle_type
>      def handle(self):
>          print "handle() from python plugin"

BR
Renato Araujo Oliveira Filho




On Fri, Aug 7, 2009 at 3:54 PM, Nodir GULYAMOV<gelvaos at gmail.com> wrote:
> Hello All,
> I am trying to implement plug-ins system using BOOST Python but a little
> stuck. I've read documentation a couple of times and have feeling that
> missed something pretty simple.
> Below simplified version what I am trying to do:
>
> // abstract Base interface class
> class IBasePlugins
> {
> public:
>    virtual ~IBasePlugins() {};
>    virtual bool canHandle(int type) = 0;
>    virtual void handle() = 0;
> };
>
> //some C++ internal plugin (no need to expose to python)
> class IntrPlugin : public IBasePlugins
> {
> public:
>    IntrPlugin() : handle_type(1) {}
>    bool canHandle(int type) {
>         return type == handle_type;
>    }
>    void handle() {
>         std::cout << "handle() from internal plugin" << std::endl;
>    }
> private:
>    int handle_type;
> };
>
>
> // class to manage plug-ins
>
> typedef boost::shared_ptr<IPlugins> PluginsPtrType;
> typedef vector<PluginsPtrType> VPluginsType;
>
> class PluginsMgr
> {
> public:
>    static void register(PluginsPtrType plugin) {
>        vplugins.puch_back(plugin);
>    }
>    static void run(int type) {
>       VPluginsType::iterator it;
>       for(it = vplugins.begin(); it != vplugins.end(); it++)
>           if( (*it)->canHandle(type) ) (*it)->handle();
>    }
> private:
>   VPluginsType vplugins;
> };
>
> // export to python
> struct IBasePluginsWrap : public IBasePlugins {
>        IBasePluginsWrap(PyObject* self_): self(self_) {}
>        bool canHandle(int type) {
>            return call_method< bool >(self, "canHandle", type);
>        }
>        void handle() {
>            call_method< void >(self, "handle");
>        }
>
>        PyObject* self;
> };
>
> BOOST_PYTHON_MODULE(pyPlugins)
> {
>    class_< IBasePlugins, IBasePluginsWrap, boost::noncopyable >("IBasePlugins")
>        .def("canHandle", pure_virtual(&IBasePlugins::canHandle))
>        .def("handle", pure_virtual(&IBasePlugins::handle))
>        ;
>
>    class_< PluginsMgr >("PluginsMgr")
>        .def("registerPlugin", &PlgMgr::registerPlugin)
>        .staticmethod("registerPlugin")
>        .def("run", &PlgMgr::run)
>        .staticmethod("run")
>        ;
>
>    register_ptr_to_python<PluginsPtrType>();
> }
>
>
> Then I am using it from python as follows:
>
> from pyPlugins import *
>
> class PyTestPlugin(IBasePlugins):
>      def __init__(self):
>          self.handle_type = 2
>      def canHandle(self, type):
>          return type == handle_type
>      def handle(self):
>          print "handle() from python plugin"
>
>
> pm = PluginsMgr()
> testplg = PyTestPlugin()
> pm.registerPlugin(testplg)
>
> And have error that C++ signature mismatch.
>
> Thank you in advance. I will really appreciate any help.
>
> Kind regards,
> Nodir
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