boost property tree: How to delete the specified parameters of the node

Question

<root>
    <stu id="1">
        <name>a</name>
    </stu>
    <stu id="2">
        <name>b</name>
    </stu>
    <stu id="3">
        <name>c</name>
    </stu>
</root>

I want to delete the id = 2 node. I use

boost::property_tree::ptree pt;
pt.erase(Node);

But this will remove all the Node

Answer 1

Assuming you didn't have problems deleting the attribute, here's fighting to the solution using Boost Property Tree:

Live On Coliru

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

using boost::property_tree::ptree;
static auto const pretty = boost::property_tree::xml_writer_make_settings<std::string>(' ', 4);

template <typename Tree>
auto find_children(Tree& pt, std::string const& key) {
    std::vector<typename Tree::iterator> matches;

    for (auto it = pt.begin(); it != pt.end(); ++it)
        if (it->first == key)
            matches.push_back(it);

    return matches;
}

int main() {
    ptree pt;
    {
        std::istringstream iss(R"(<root><stu id="1"><name>a</name></stu><stu id="2"><name>b</name></stu><stu id="3"><name>c</name></stu></root>)");
        read_xml(iss, pt);
    }

    auto& root = pt.get_child("root");

    for (auto stu : find_children(root, "stu")) {
        if (2 == stu->second.get("<xmlattr>.id", -1)) {
            std::cout << "Debug: erasing studen " << stu->second.get("name", "N.N.") << "\n";
            root.erase(stu);
        }
    }

    write_xml(std::cout, pt, pretty);
}

Printing:

Debug: erasing student b
<?xml version="1.0" encoding="utf-8"?>
<root>
    <stu id="1">
        <name>a</name>
    </stu>
    <stu id="3">
        <name>c</name>
    </stu>
</root>

Using An XML Library

Of course, using an XML library is much easier:

#include <iostream>
#include <pugixml.hpp>

int main() {
    pugi::xml_document doc;
    doc.load_string(R"(<root><stu id="1"><name>a</name></stu><stu id="2"><name>b</name></stu><stu id="3"><name>c</name></stu></root>)");

    for (auto& n : doc.select_nodes("//root/stu[@id=2]")) {
        auto node = n.node();
        node.parent().remove_child(node);
    }

    pugi::xml_writer_stream w(std::cout);
    doc.save(w);
}