Compilation error with boost::property_tree::xml_writer_settings

Question

In order to pretty print my XML output with boost::property_tree, I wrote the following code:

#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>

int main()
{
    std::string filename = "test.xml";
    boost::property_tree::ptree pt;
    pt.put("some.path.value", "hello");

    boost::property_tree::xml_writer_settings<char> settings('\t', 1);
    write_xml(filename, pt, settings);
}

Unfortunately I have this error and I can't find any information about it:

/usr/local/include/boost/property_tree/detail/xml_parser_writer_settings.hpp:38:19: error: type 'char' cannot be used prior to '::' because it has no members
    typedef typename Str::value_type Ch;
                     ^

Any idea?

Yukyukaghir

This document may help you, but I'm not sure – Kela

this is the header I'm using – Yukyukaghir

Next time: Please include relevant code in the question, so we can ace the answer, instead of drawing out "thanks but..." in the comments :) – Aparejo

Yes I will add it right now – Yukyukaghir

Answer 1

I'd use the helper function

std::ofstream file("test.xml");

boost::property_tree::ptree pt;    
pt.put("some.value", "test");

boost::property_tree::write_xml(
   file, pt,
   boost::property_tree::xml_writer_make_settings<std::string>('\t', 1));

Aparejo

It works but how can I use it with write_xml? When writing write_xml(filename, pt, boost::property_tree::xml_writer_make_settings<std::string>('\t', 1)) I have the following error: no matching function for call to 'write_xml – Yukyukaghir

@MartinDelille You need to pass a stream, not a filename. The documentation is patient :) boost.org/doc/libs/1_57_0/doc/html/boost/property_tree/… (also funny you truncated the message because now I'm having to guess what the types of filename and pt are). – Aparejo

There is an issue with changing from <char> to <std::string> it only works if you are building on a 64bit, otherwise if you are building on 32bit and try to use <std::string> then you will get above described error, however if you are building on 64bit you will not get the error -- this assuming that you used a stream and not filename – Restriction

@Restriction that makes little sense. It seems like you may be conflating character encoding and build architecture. – Aparejo

@sehe, I agree it makes little sense, none the less it is the fact - try it out – Restriction