Boost Python没有为std :: string找到to_python转换器 [英] Boost Python No to_python converter found for std::string

问题描述

因此，我正在尝试创建一个to_python转换器，该转换器将允许我从公开的函数返回boost :: optional，如果设置了optional，则将其视为T；否则将其视为None.基于我在 C ++ Sig 上找到的帖子中，我编写了以下代码.

So, I am trying to create a to_python converter that will allow me to return a boost::optional from an exposed function and have it treated as T if the optional is set and None if not. Based on a post I found on C++Sig, I wrote the following code.

template<typename T>
struct optional_ : private boost::noncopyable {
  struct conversion {
    static PyObject* convert(boost::optional<T> const& value) {
      if (value) {
        return boost::python::to_python_value<T>()(*value);
      }
      Py_INCREF(Py_None);
      return Py_None;
    }
  };
  explicit optional_() {
    boost::python::to_python_converter<boost::optional<T>, conversion>();
  }
};

据我所知，它可用于转换可选内容，但是python引发以下异常"TypeError:找不到C ++类型的to_python(按值)转换器:std :: string".我知道C ++能够将字符串转换为python，因为我的大多数公开函数都返回字符串.为什么boost :: python :: to_python_value无法识别它，我该如何利用它具有的任何转换器?

As far as I can tell, it works for converting the optionals, but python throws the following exception "TypeError: No to_python (by-value) converter found for C++ type: std::string". I know that C++ is able to convert strings to python since most of my exposed functions return strings. Why doesn't boost::python::to_python_value recognize it, and how can I utilize whatever converter it has?

通过更改为以下内容进行修复(基于

Fixed by changing to the following (based on this article):

template<typename T>
struct optional_ : private boost::noncopyable {
  struct conversion {
    static PyObject* convert(boost::optional<T> const& value) {
      using namespace boost::python;
      return incref((value ? object(*value) : object()).ptr());
    }
  };
  explicit optional_() {
    boost::python::to_python_converter<boost::optional<T>, conversion>();
  }
};

现在只做其他版本，以便它更干净，更好地工作.

Now to just do the other version so that it is cleaner and works better.

推荐答案

好吧，这是基于原始C ++ sig帖子的来回可选转换器的全部内容，但重写后使用了高级boost.python API(对不起，很奇怪间距).

Ok here is the entire to and from optional converter based on the original C++ sig post but rewritten to use the high level boost.python API (sorry about the weird spacing).

template<typename T>
struct optional_ : private boost::noncopyable
{
  struct conversion :
    public boost::python::converter::expected_from_python_type<T>
  {
    static PyObject* convert(boost::optional<T> const& value) {
      using namespace boost::python;
      return incref((value ? object(*value) : object()).ptr());
    }
  };

  static void* convertible(PyObject *obj) {
    using namespace boost::python;
    return obj == Py_None || extract<T>(obj).check() ? obj : NULL;
  }

  static void constructor(PyObject *obj,
       boost::python::converter::rvalue_from_python_stage1_data *data)
  {
    using namespace boost::python;
    void *const storage =
      reinterpret_cast<
        converter::rvalue_from_python_storage<boost::optional<T> >*
      >(data)->storage.bytes;
    if(obj == Py_None) {
      new (storage) boost::optional<T>();
    } else {
      new (storage) boost::optional<T>(extract<T>(obj));
    }
    data->convertible = storage;
  }

  explicit optional_() {
    using namespace boost::python;
    if(!extract<boost::optional<T> >(object()).check()) {
      to_python_converter<boost::optional<T>, conversion, true>();
      converter::registry::push_back(
        &convertible,
        &constructor,
        type_id<boost::optional<T> >(),
        &conversion::get_pytype
      );
    }
  }
};

这篇关于Boost Python没有为std :: string找到to_python转换器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！