C++:提升 ptree 相对键

C++: boost ptree relative key

本文关键字：相对 ptree 提升 C++      更新时间：2023-10-16

在C++使用来自boostptree时，我需要找到从a.b访问a.b.c2.e1的相对键。此密钥为c2.e1。如何编写一个找到此相对键的函数？

#include <iostream>
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
using namespace boost::property_tree;
std::string relative_key(const ptree &p1,const ptree &p2)
{
??????????????
// return "b.c2.e1";
}
int main()
{
ptree pt0;
pt0.put("a.b.c1",4);
pt0.put("a.b.c2.e1",4);
pt0.put("a.b.c4",4);
pt0.put("a.d",4);
pt0.put("k.m",4);
pt0.put("k.n",4);
ptree &pt_e1=pt0.get_child("a.b.c2.e1");
ptree &pt_b=pt0.get_child("a.b");
std::cout<<relative_key(pt_e1,pt_b)<<std::endl;
return 0;
}

你需要编写一个递归搜索函数，比如：

bool find_subtree_helper(ptree const& haystack, ptree const& needle, path_type& path) {
if (std::addressof(haystack) == std::addressof(needle))
return true;
for (auto& child : haystack) {
auto next = path;
next /= child.first;
if ( std::addressof(child.second) == std::addressof(needle) 
|| find_subtree_helper(child.second, needle, next))
{
path = next;
return true;
}
}
return false;
}
path_type find_subtree(ptree const& haystack, ptree const& needle) {
path_type path;
if (!find_subtree_helper(haystack, needle, path))
throw std::range_error("not subtree");
return path;
}

像这样使用它：

住在科里鲁

path_type p = find_subtree(pt_b, pt_e1);
std::cout << p.dump() << std::endl;

打印"c2.e1"。

完整列表

住在科里鲁

#include <iostream>
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
using namespace boost::property_tree;
using path_type = ptree::path_type;
bool find_subtree_helper(ptree const& haystack, ptree const& needle, path_type& path) {
if (std::addressof(haystack) == std::addressof(needle))
return true;
for (auto& child : haystack) {
auto next = path;
next /= child.first;
if ( std::addressof(child.second) == std::addressof(needle) 
|| find_subtree_helper(child.second, needle, next))
{
path = next;
return true;
}
}
return false;
}
path_type find_subtree(ptree const& haystack, ptree const& needle) {
path_type path;
if (!find_subtree_helper(haystack, needle, path))
throw std::range_error("not subtree");
return path;
}
int main()
{
ptree pt0;
pt0.put("a.b.c1",4);
pt0.put("a.b.c2.e1",4);
pt0.put("a.b.c4",4);
pt0.put("a.d",4);
pt0.put("k.m",4);
pt0.put("k.n",4);
ptree &pt_e1 = pt0.get_child("a.b.c2.e1");
ptree &pt_b  = pt0.get_child("a.b");
path_type p = find_subtree(pt_b, pt_e1);
std::cout << p.dump() << std::endl;
}
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