Adding a sub child to boost ptree

Question

Lets say I am aiming to create an xml in the following form:

<main>
<elements>
    <element name="elem1"><temp/>
    </element>
    <element name="elem2"><temp/>
    </element>
</elements>
</main>

I have the following code:

ptree pt;
pt.put("main","");

ptree temp1;
temp1.put("element","");
temp1.put("element.<xmlattr>.name","elem1");
temp1.put("element.temp");

ptree temp2;
temp2.put("element","");
temp2.put("element.<xmlattr>.name","elem2");
temp2.put("element.temp");

//temp1 represents the 1st <element>...</element>
//temp2 represents the 1st <element>...</element>

//Add temp1 and temp2 to <main> under <elements>

I would assume the following would work:

pt.add_child("main.elements",temp1);
pt.add_child("main.elements",temp2);

However this generates the following xml:

<main>
<elements>
    <element name="elem1"><temp/>
    </element>
</elements>
<elements>
    <element name="elem2"><temp/>
    </element>
<elements>
</main>

I was able to get the required xml file by making my temp1 in the following form:

temp1.put("<xmlattr>.name","elem1");
temp1.put("temp","");
temp2.put("<xmlattr>.name","elem2");
temp2.put("temp","");
pt.add_child("main.elements.element",temp1);
pt.add_child("main.elements.element",temp2);

Is there a way I can work with my initial temp1 and temp2 nodes to get the desired xml structure?

Answer 1

Your situation is a bit suboptimal (and I'd very much favour the working snippet you gave).

Here's what would work:

pt.add_child("main.elements.element", temp1.get_child("element"));
pt.add_child("main.elements.element", temp2.get_child("element"));

Live On Coliru

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

using boost::property_tree::ptree;

int main() {
    ptree temp1;
    temp1.put("element.<xmlattr>.name","elem1");
    temp1.put_child("element.temp", {});

    ptree temp2;
    temp2.put("element.<xmlattr>.name","elem2");
    temp2.put("element.temp", "");

    //Add temp1 and temp2 to <main> under <elements>
    ptree pt;
    pt.add_child("main.elements.element", temp1.get_child("element"));
    pt.add_child("main.elements.element", temp2.get_child("element"));
    write_xml(std::cout, pt, boost::property_tree::xml_writer_make_settings<std::string>(' ', 4, "utf-8"));
}

Prints

<?xml version="1.0" encoding="utf-8"?>
<main>
    <elements>
        <element name="elem1">
            <temp/>
        </element>
        <element name="elem2">
            <temp/>
        </element>
    </elements>
</main>