[Boost-users] Property Tree

From: Glasgow, Craig C (Craig.Glasgow_at_[hidden])
Date: 2008-01-23 06:24:05

Hello
I'm using boost property_tree with the variant data type:
typedef boost::variant<std::string, std::vector<std::string> >
registry_entry;
i.e I want to store either strings or vectors of strings at each key
node. I'm using the inserters and extractors at the bottom of this email
(similar to those included in the custom_data.cpp in the
property_tree/examples folder).  

Does anyone know how I can write the tree out in xml format? The
provided write_xml method can only handle property trees of string data
type. Is there anyway to either tweak the code (e.g. modify the inserter
and extractors) or wrap the variant class such that
property_tree::write_xml will correctly render the tree as xml? 

Regards
Craig

// Custom extractor - converts data from boost::any to Type
template<class Type>
struct pt_extractor
{
    inline bool operator()(const boost::any &data, 
                           Type &extracted,
                           const std::locale &loc) const
    {
        extracted = boost::any_cast<Type>(data);
        return true;    // Success
    }
};

// Custom inserter - converts data from Type to boost::any
template<class Type>
struct pt_inserter
{
    inline bool operator()(boost::any &data,
                           const Type &to_insert,
                           const std::locale &loc) const
    {
        data = to_insert;
        return true;    // Success
    }
};

// Custom property_tree traits - using custom extractor and inserter
template<class Ch>
struct pt_traits
{

    // Character type to be used by ptree keys
    typedef Ch char_type;

    // Key type to be used by ptree
    typedef std::basic_string<Ch> key_type;

    // Data type to be used by ptree
    typedef boost::any data_type;
    
    // Extractor to be used by ptree
    template<class Type>
    struct extractor: public pt_extractor<Type> { }; 

    // Inserter to be used by ptree
    template<class Type>
    struct inserter: public pt_inserter<Type> { };

    // Key comparison function
    inline bool operator()(const key_type &key1, 
                           const key_type &key2) const
    {
                return _stricmp(key1.c_str(), key2.c_str()) < 0;
    }

};

typedef boost::property_tree::basic_ptree<pt_traits<char> > pt_rep;
typedef boost::variant<std::string, std::vector<std::string> >
registry_entry;

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