是否可以在boost :: property_tree中添加boost :: any？

Question

我正在嘗試將boost ::: any類型存儲到boost屬性樹。 這是一些可運行的示例：

#include <string>
#include <vector>
#include <sstream>
#include <iostream>
#include <sys/types.h>
#include <boost/any.hpp>
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>

int main()
{
    boost::property_tree::ptree pTree_Root;
    pTree_Root.put("sigRoot.property1", "value1");
    pTree_Root.put("sigRoot.property2", "value2");
    pTree_Root.put("sigRoot.property3", "value3");

    std::vector<std::string> vecString;

    for(int i = 0; i <= 5; i++) {
        vecString.push_back("somestring");
    }

    boost::any anyVar = vecString;

    pTree_Root.put("sigRoot.property4", anyVar);

    std::stringstream ss;
    boost::property_tree::json_parser::write_json(ss, pTree_Root);
    std::string jsonString = ss.str();

    jsonString.erase(std::remove(jsonString.begin(), jsonString.end(), '\n'), jsonString.end());

    std::cout << jsonString << std::endl;

  return 0;
}

這不起作用，可能出於同樣的原因boost :: any不可序列化。 但是我看到我可以查詢anyVar.type() ，但是我不知道該怎么辦。 是否可以以某種方式使用auto或其他方式將數據添加到屬性樹，而無需在此處顯式編碼固定數量的已知類型？ 也歡迎使用C ++ 11 / C ++ 0x方法。

這是我得到的錯誤：

In file included from /usr/include/boost/property_tree/ptree.hpp:17:0,
                 from pTreeTest.cpp:8:


/usr/include/boost/property_tree/stream_translator.hpp: In static member function ‘static void boost::property_tree::customize_stream<Ch, Traits, E, Enabler>::insert(std::basic_ostream<_Ch, _Tr>&, const E&) [with Ch = char, Traits = std::char_traits<char>, E = boost::any, Enabler = void]’:
/usr/include/boost/property_tree/stream_translator.hpp:199:13:   instantiated from ‘boost::optional<std::basic_string<Ch, Traits, Alloc> > boost::property_tree::stream_translator<Ch, Traits, Alloc, E>::put_value(const E&) [with Ch = char, Traits = std::char_traits<char>, Alloc = std::allocator<char>, E = boost::any]’
/usr/include/boost/property_tree/detail/ptree_implementation.hpp:795:54:   instantiated from ‘void boost::property_tree::basic_ptree<Key, Data, KeyCompare>::put_value(const Type&, Translator) [with Type = boost::any, Translator = boost::property_tree::stream_translator<char, std::char_traits<char>, std::allocator<char>, boost::any>, Key = std::basic_string<char>, Data = std::basic_string<char>, KeyCompare = std::less<std::basic_string<char> >]’
/usr/include/boost/property_tree/detail/ptree_implementation.hpp:817:13:   instantiated from ‘boost::property_tree::basic_ptree<K, D, C>& boost::property_tree::basic_ptree<Key, Data, KeyCompare>::put(const path_type&, const Type&, Translator) [with Type = boost::any, Translator = boost::property_tree::stream_translator<char, std::char_traits<char>, std::allocator<char>, boost::any>, Key = std::basic_string<char>, Data = std::basic_string<char>, KeyCompare = std::less<std::basic_string<char> >, boost::property_tree::basic_ptree<Key, Data, KeyCompare>::path_type = boost::property_tree::string_path<std::basic_string<char>, boost::property_tree::id_translator<std::basic_string<char> > >]’
/usr/include/boost/property_tree/detail/ptree_implementation.hpp:832:72:   instantiated from ‘boost::property_tree::basic_ptree<K, D, C>& boost::property_tree::basic_ptree<Key, Data, KeyCompare>::put(const path_type&, const Type&) [with Type = boost::any, Key = std::basic_string<char>, Data = std::basic_string<char>, KeyCompare = std::less<std::basic_string<char> >, boost::property_tree::basic_ptree<Key, Data, KeyCompare>::path_type = boost::property_tree::string_path<std::basic_string<char>, boost::property_tree::id_translator<std::basic_string<char> > >]’



pTreeTest.cpp:26:47:   instantiated from here
/usr/include/boost/property_tree/stream_translator.hpp:33:13: error: cannot bind ‘std::basic_ostream<char>’ lvalue to ‘std::basic_ostream<char>&&’
/usr/include/c++/4.6/ostream:581:5: error:   initializing argument 1 of ‘std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT = char, _Traits = std::char_traits<char>, _Tp = boost::any]’

Answer 1

號boost::any沒有operator << 。 您不能在property_tree使用any 。 anyVar.type()返回std::typeinfo ，此類提供有關類型的runtime信息。

template<typename Type, typename Translator> 
  self_type & put(const path_type & path, const Type & value, Translator tr);

將給定路徑上節點的值設置為提供的值，將其轉換為樹的數據類型。 如果該節點不存在，則會創建該節點，包括所有缺少的父節點。

您可以創建Translator並將其傳遞給put函數，因為ptree實際上是basic_ptree<std::string, std::string>您的翻譯器應將any轉換為string 。

譯者的簡單例子

struct SimpleTranslator
{
public:
   boost::optional<std::string> put_value(const boost::any& value)
   {
      if (value.type() == typeid(std::vector<std::string>))
      {
         std::stringstream ss;
         std::vector<std::string> vec = boost::any_cast<std::vector<std::string>>(value);
         std::copy(vec.begin(), vec.end(), std::ostream_iterator<std::string>(ss));
         return ss.str();
      }
      return boost::optional<std::string>();
   }
};

http://liveworkspace.org/code/275820c1becfb63deda4e4eed8524833