C++：boost ptree 删除子项：没有匹配的函数

Question

In an attempt to remove children of a boost property tree, I use a direct node in erase function which lead to

error: no matching function for call to 
‘boost::property_tree::basic_ptree<std::__cxx11::basic_string<char>, 
std::__cxx11::basic_string<char> >::erase(std::pair<const 
std::__cxx11::basic_string<char>, 
boost::property_tree::basic_ptree<std::__cxx11::basic_string<char>, 
std::__cxx11::basic_string<char> > >&)’

at

pt0.erase(pt_child);

What is the correct form of the code?

#include <iostream>
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>

using namespace boost::property_tree;

void print(const ptree &p)
{
    json_parser::write_json(std::cout, p);
}

int main()
{
    ptree pt0;

    for(int i=0;i<10;i++)
        pt0.put_child("kid"+std::to_string(i+1),ptree());
    print(pt0);

    for(auto& pt_child : pt0)
        pt0.erase(pt_child);
    print(pt0);

    return 0;
}

Answer 1

You could do this:ptree.get_child("path.to").erase("child"); Note that this deletes ALL nodes named "child" within the path "path.to" and their subchildren.

Answer 2

It's unfortunate but the ptree api doesn't have a remove_child method that works with a property_tree::path just like it does for get_child . Here's a small method that does that though. The important part is that you can use the dot notation to specify whatever subchild you want to remove. Also this implementation only removes a single child.

#include <boost/property_tree/ptree.hpp>
#include <boost/algorithm/string.hpp>

// TODO: this should support boost::property_tree::path
// like get_child does to make it obvious that it supports
// the path separator notation for specifying sub children
bool remove_child(boost::property_tree::ptree& pt, const std::string& path) {
  // split up the path into each sub part
  std::vector<std::string> path_parts;
  boost::split(path_parts, path, boost::is_any_of("."));

  // check each part of the path
  auto* root = &pt;
  for (const auto& part : path_parts) {
    // if we dont have this sub child bail
    auto found = root->find(part);
    if (found == root->not_found())
      return false;

    // if this was the last one to look for remove it
    if (&part == &path_parts.back()) {
      root->erase(root->to_iterator(found));
    }// next sub child
    else {
      root = &found->second;
    }
  }

  // made it to the last sub child without bailing on not found
  return true;
}

Answer 3

According to docs you can only .erase by key_type or by iterator , but you are trying to do it by value_type .

You can do either do

for(auto& [key, data]: pt0)
    pt0.erase(key);

or loop over iterators explicitly:

for(auto it = pt0.begin(); it != pt0.end(); ++it)
    pt0.erase(it);

But since you are removing all children anyway, a better way would be to just

pt0.clear();