Cpp CookBook.md

If you call

xml_file.get_child("assignments")

on this XML

<assignments clear_all="false">
    <button nr="19" dataref="ELEVATOR TRIM POSITION%Radians" type="trigger_pos" on="0" />
    <button nr="18" command="ELEV_TRIM_UP" type="trigger_pos" >
    </button>
    <button nr="17" command="ELEV_TRIM_DOWN" type="trigger_pos" />
</assignments>

then it will be translated into a ptree looking like this

<xmlattr>
{
    clear_all false
}
button  ;'button' key (no data inside the opening and closing tag)
{
    <xmlattr>	;special <xmlattr> subkey (no data)
    {
        nr 19   ;'nr' attribute and its value
        dataref "ELEVATOR TRIM POSITION%Radians"
        type "trigger_pos"
        on = "0"
    }
}
button
{
    <xmlattr>
    {
        nr 18
        dataref "ELEV_TRIM_UP"
        type "trigger_pos"
    }
}
button
{
    <xmlattr>
    {
        nr 17
        dataref "ELEV_TRIM_DOWN"
        type "trigger_pos"
    }
}

Write XML file starting from a value_type of only attributes by reconstructing the element.

boost::property_tree::ptree pt;
pt.add_child("button", xmltree.second);
boost::property_tree::write_xml("testXml.xml", pt, std::locale());

ptree::value_type is defined like typedef std::pair< const Key, self_type> value_type; so it is essentially a std::pair. Source: How do we get objects in boost property tree

value_type.first is the name of the tag

value_type.second is the ptree below this element, the children of this element (StackOverflow Boost Property_Tree iterators, how to handle them?)

StackOverflow How to iterate a boost property tree? Mentions for (auto& it: tree) at the end since C++11. Also mentions ptree::const_iterator.

Boost 1.46.1, Property Tree: How to iterate through ptree receiving sub ptrees? says „With C++17 you can do it even more elegant with structured bindings: for (const auto& [key, value] : children) { ... }”

Older but a bit better doc of ptree: http://kaalus.atspace.com/ptree/doc/index.html