I've been trying to use some of the boost fusion stuff to write a regular c struct to file. An XML file seems a good way to capture the data and make it compatible with other tools or hand editable. It seems like I almost have it but something fundamental seems to be missing. I'm using something pretty similar to what's on the boost::fusion quick start page: http://www.boost.org/doc/libs/1_54_0/libs/fusion/doc/html/fusion/quick_start.html. As a side note I have thoroughly looked here and on boost's documentation but no one seems to be accessing the field name.
struct print_xml
{
template <typename T>
void operator()(T const& x) const
{
std::cout
<< '<' << x.first << '>'
<< x
<< "</" << x.first << '>'
;
}
};
I want to use it as follows:
BOOST_FUSION_ADAPT_STRUCT(
myStructType,
(double, val1)
(double, val2)
(char, letter)
(int, number)
)
myStructType saveMe = { 3.4, 5.6, 'g', 9};
for_each(saveMe, print_xml());
Other times I defined the struct as follows, but still no luck:
namespace fields{
struct val1;
struct val2;
struct letter;
struct number;
}
typedef fusion::map<
fusion::pair<fields::val1, double>,
fusion::pair<fields::val2, double>,
fusion::pair<fields::letter, char>,
fusion::pair<fields::number, int> > myStructType;
I know there is no member first, but it really seems like there should be in order to access the field name! The code I have works fine with x.second but then doesn't accomplish what I need which is to get the field name. How else might I accomplish this? Thanks!
#include <iostream>
#include <string>
#include <boost/mpl/range_c.hpp>
#include <boost/fusion/include/for_each.hpp>
#include <boost/fusion/include/zip.hpp>
#include <boost/fusion/include/at_c.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/mpl.hpp>
namespace fusion=boost::fusion;
namespace mpl=boost::mpl;
struct myStructType
{
double val1;
double val2;
char letter;
int number;
};
BOOST_FUSION_ADAPT_STRUCT(
myStructType,
(double, val1)
(double, val2)
(char, letter)
(int, number)
)
template <typename Sequence>
struct XmlFieldNamePrinter
{
XmlFieldNamePrinter(const Sequence& seq):seq_(seq){}
const Sequence& seq_;
template <typename Index>
void operator() (Index idx) const
{
//use `Index::value` instead of `idx` if your compiler fails with it
std::string field_name = fusion::extension::struct_member_name<Sequence,idx>::call();
std::cout
<< '<' << field_name << '>'
<< fusion::at<Index>(seq_)
<< "</" << field_name << '>'
;
}
};
template<typename Sequence>
void printXml(Sequence const& v)
{
typedef mpl::range_c<unsigned, 0, fusion::result_of::size<Sequence>::value > Indices;
fusion::for_each(Indices(), XmlFieldNamePrinter<Sequence>(v));
}
int main()
{
myStructType saveMe = { 3.4, 5.6, 'g', 9};
printXml(saveMe);
}
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