Boost::property_tree: 在 XML 解析器中使用 std::vector<> 将多个值存储在一个键中
Boost::property_tree: Using std::vector<> in XML parser to store multiple values in one key
我的问题与这个问题有关:Boost property_tree: multiple values per key and to a question following that question: Boost property_tree: multiple values per key, on a template class。
我正在尝试解析一个 XML 文件,其中使用 std::vector<>
在单个键值处列出了多个值。下面的代码是我目前实现的:
#include <boost/optional.hpp>
#include <boost/property_tree/xml_parser.hpp>
namespace boost { namespace property_tree
{
template<typename type>
struct vector_xml_translator
{
boost::optional<std::vector<type> > get_value(const std::string& str)
{
if (!str.empty())
{
std::vector<type> values;
std::stringstream ss(str);
while (ss)
{
type temp_value;
ss >> temp_value;
values.push_back(temp_value);
}
return boost::optional<std::vector<type> >(values);
}
else
{
return boost::optional<std::vector<type> >(boost::none);
}
}
boost::optional<std::string> put_value(const std::vector<type>& b)
{
std::stringstream ss;
for (unsigned int i = 0; i < b.size(); i++)
{
ss << b[i];
if (i != b.size()-1)
{
ss << " ";
}
}
return boost::optional<std::string>(ss.str());
}
};
template<typename ch, typename traits, typename alloc, typename data_type>
struct translator_between<std::basic_string<ch, traits, alloc>, std::vector<data_type> >
{
typedef vector_xml_translator<data_type> type;
};
} // namespace property_tree
} // namespace boost
测试此代码的最小示例如下:
#include <fstream>
#include <iostream>
#include <boost/property_tree/ptree.hpp>
#include <XML_Vector_Translator.hpp>
int main()
{
using boost::property_tree::ptree;
std::vector<double> test_vector;
test_vector.push_back(1);
test_vector.push_back(6);
test_vector.push_back(3);
ptree pt;
pt.add("base", test_vector);
std::ofstream os("test_file.xml");
write_xml(os, pt, boost::property_tree::xml_writer_settings<std::string>(' ', 2));
std::ifstream is("test_file.xml");
ptree pt_2;
read_xml(is, pt_2);
std::vector<int> test_vector_2;
test_vector_2 = pt_2.get<std::vector<int> >("base");
for (unsigned int i = 0; i < test_vector_2.size(); i++)
{
std::cout << test_vector_2[i] << std::endl;
}
return 0;
}
当我运行这段代码时,我得到了一些错误,这让我相信翻译器结构的注册是不正确的。有没有人知道如何解决这个问题 and/or 改进这段代码?
正如较早的答案也指出的那样¹您必须满足 boost::property_tree::detail::is_translator
的要求,因此您需要 internal_type
/ external_type
typedefs.
typedef T internal_type;
typedef T external_type;
接下来,循环错误,需要检查取值结果:
while (ss >> temp_value)
values.push_back(temp_value);
将您自己的类型放在 boost 命名空间中是不好的做法。只有 translator_between<>
的专业化需要在那里。
你可以简化和概括很多代码
全部在工作演示中:
#include <boost/optional.hpp>
#include <boost/property_tree/ptree.hpp>
#include <vector>
#include <list>
namespace mylib { namespace xml_translators {
template<typename T> struct container
{
// types
typedef T internal_type;
typedef T external_type;
boost::optional<T> get_value(const std::string& str) const
{
if (str.empty())
return boost::none;
T values;
std::stringstream ss(str);
typename T::value_type temp_value;
while (ss >> temp_value)
values.insert(values.end(), temp_value);
return boost::make_optional(values);
}
boost::optional<std::string> put_value(const T& b) {
std::stringstream ss;
size_t i = 0;
for (auto v : b)
ss << (i++?" ":"") << v;
return ss.str();
}
};
} }
namespace boost { namespace property_tree {
template<typename ch, typename traits, typename alloc, typename T>
struct translator_between<std::basic_string<ch, traits, alloc>, std::vector<T> > {
typedef mylib::xml_translators::container<std::vector<T> > type;
};
template<typename ch, typename traits, typename alloc, typename T>
struct translator_between<std::basic_string<ch, traits, alloc>, std::list<T> > {
typedef mylib::xml_translators::container<std::list<T> > type;
};
} }
#include <sstream>
#include <iostream>
#include <boost/property_tree/xml_parser.hpp>
int main()
{
std::stringstream ss;
using boost::property_tree::ptree;
{
ptree pt;
pt.add("base", std::vector<double> { 1, 6, 3 });
write_xml(ss, pt, boost::property_tree::xml_writer_settings<std::string>(' ', 2));
}
{
ptree pt;
read_xml(ss, pt);
std::cout << "As string: '" << pt.get("base", "") << "'\n";
auto roundtrip = pt.get<std::list<int> >("base");
for (auto i : roundtrip)
std::cout << i << std::endl;
}
}
版画
As string: '1 6 3'
1
6
3
¹ Boost property_tree: multiple values per key, see also the identity translator http://www.boost.org/doc/libs/1_64_0/doc/html/boost/property_tree/id_translator.html
我的问题与这个问题有关:Boost property_tree: multiple values per key and to a question following that question: Boost property_tree: multiple values per key, on a template class。
我正在尝试解析一个 XML 文件,其中使用 std::vector<>
在单个键值处列出了多个值。下面的代码是我目前实现的:
#include <boost/optional.hpp>
#include <boost/property_tree/xml_parser.hpp>
namespace boost { namespace property_tree
{
template<typename type>
struct vector_xml_translator
{
boost::optional<std::vector<type> > get_value(const std::string& str)
{
if (!str.empty())
{
std::vector<type> values;
std::stringstream ss(str);
while (ss)
{
type temp_value;
ss >> temp_value;
values.push_back(temp_value);
}
return boost::optional<std::vector<type> >(values);
}
else
{
return boost::optional<std::vector<type> >(boost::none);
}
}
boost::optional<std::string> put_value(const std::vector<type>& b)
{
std::stringstream ss;
for (unsigned int i = 0; i < b.size(); i++)
{
ss << b[i];
if (i != b.size()-1)
{
ss << " ";
}
}
return boost::optional<std::string>(ss.str());
}
};
template<typename ch, typename traits, typename alloc, typename data_type>
struct translator_between<std::basic_string<ch, traits, alloc>, std::vector<data_type> >
{
typedef vector_xml_translator<data_type> type;
};
} // namespace property_tree
} // namespace boost
测试此代码的最小示例如下:
#include <fstream>
#include <iostream>
#include <boost/property_tree/ptree.hpp>
#include <XML_Vector_Translator.hpp>
int main()
{
using boost::property_tree::ptree;
std::vector<double> test_vector;
test_vector.push_back(1);
test_vector.push_back(6);
test_vector.push_back(3);
ptree pt;
pt.add("base", test_vector);
std::ofstream os("test_file.xml");
write_xml(os, pt, boost::property_tree::xml_writer_settings<std::string>(' ', 2));
std::ifstream is("test_file.xml");
ptree pt_2;
read_xml(is, pt_2);
std::vector<int> test_vector_2;
test_vector_2 = pt_2.get<std::vector<int> >("base");
for (unsigned int i = 0; i < test_vector_2.size(); i++)
{
std::cout << test_vector_2[i] << std::endl;
}
return 0;
}
当我运行这段代码时,我得到了一些错误,这让我相信翻译器结构的注册是不正确的。有没有人知道如何解决这个问题 and/or 改进这段代码?
正如较早的答案也指出的那样¹您必须满足
boost::property_tree::detail::is_translator
的要求,因此您需要internal_type
/external_type
typedefs.typedef T internal_type; typedef T external_type;
接下来,循环错误,需要检查取值结果:
while (ss >> temp_value) values.push_back(temp_value);
将您自己的类型放在 boost 命名空间中是不好的做法。只有
translator_between<>
的专业化需要在那里。你可以简化和概括很多代码
全部在工作演示中:
#include <boost/optional.hpp>
#include <boost/property_tree/ptree.hpp>
#include <vector>
#include <list>
namespace mylib { namespace xml_translators {
template<typename T> struct container
{
// types
typedef T internal_type;
typedef T external_type;
boost::optional<T> get_value(const std::string& str) const
{
if (str.empty())
return boost::none;
T values;
std::stringstream ss(str);
typename T::value_type temp_value;
while (ss >> temp_value)
values.insert(values.end(), temp_value);
return boost::make_optional(values);
}
boost::optional<std::string> put_value(const T& b) {
std::stringstream ss;
size_t i = 0;
for (auto v : b)
ss << (i++?" ":"") << v;
return ss.str();
}
};
} }
namespace boost { namespace property_tree {
template<typename ch, typename traits, typename alloc, typename T>
struct translator_between<std::basic_string<ch, traits, alloc>, std::vector<T> > {
typedef mylib::xml_translators::container<std::vector<T> > type;
};
template<typename ch, typename traits, typename alloc, typename T>
struct translator_between<std::basic_string<ch, traits, alloc>, std::list<T> > {
typedef mylib::xml_translators::container<std::list<T> > type;
};
} }
#include <sstream>
#include <iostream>
#include <boost/property_tree/xml_parser.hpp>
int main()
{
std::stringstream ss;
using boost::property_tree::ptree;
{
ptree pt;
pt.add("base", std::vector<double> { 1, 6, 3 });
write_xml(ss, pt, boost::property_tree::xml_writer_settings<std::string>(' ', 2));
}
{
ptree pt;
read_xml(ss, pt);
std::cout << "As string: '" << pt.get("base", "") << "'\n";
auto roundtrip = pt.get<std::list<int> >("base");
for (auto i : roundtrip)
std::cout << i << std::endl;
}
}
版画
As string: '1 6 3'
1
6
3
¹ Boost property_tree: multiple values per key, see also the identity translator http://www.boost.org/doc/libs/1_64_0/doc/html/boost/property_tree/id_translator.html