Method createInstance

pj_scripting/src/python_engine.cpp:214–246

  }

  Expected<std::unique_ptr<FilterInstance>> createInstance(
      const FilterClass& klass, const std::string& params_json) override {
    ensureInterpreter();
    py::gil_scoped_acquire gil;
    try {
      auto ns = std::make_shared<py::object>(py::dict());
      py::exec(klass.source, *ns);
      py::dict& nsd = reinterpret_cast<py::dict&>(*ns);
      if (!nsd.contains("T")) {
        return PJ::unexpected("Python filter module must define a top-level class named 'T'");
      }
      py::object cls = nsd["T"];
      py::object params;
      if (params_json.empty() || params_json == "{}") {
        params = py::dict();
      } else {
        params = py::module_::import("json").attr("loads")(params_json);
      }
      if (!py::hasattr(cls, "create")) {
        return PJ::unexpected("Python filter class 'T' must define a static create(params)");
      }
      py::object instance = cls.attr("create")(params);
      if (!py::hasattr(instance, "calculate")) {
        return PJ::unexpected("the object returned by T.create() must have a calculate(self, time, value) method");
      }
      return std::unique_ptr<FilterInstance>(
          std::make_unique<PythonFilterInstance>(std::move(ns), std::move(instance)));
    } catch (const py::error_already_set& e) {
      return PJ::unexpected(std::string("Python error: ") + e.what());
    } catch (const std::exception& e) {
      return PJ::unexpected(std::string("Python error: ") + e.what());
    }
  }
};

}  // namespace