從boost獲取ptree :: property_tree :: ptree :: iterator

Question

我有一段迭代遍歷boost屬性樹（XML）的代碼。
我需要當前節點的ptree，而不是節點的子節點。

UPDATE

XML樹

<node id="A.html"> 
    <subnode> child A1 </subnode> 
    <subnode> child A2 </subnode> 
</node> 

<node id="B.html"> 
    <subnode> child B1 </subnode> 
    <subnode> child B2 </subnode> 
</node> 

itteration代碼使用write_xml（ 「的test.html」，PT）

void parse_tree(ptree& pt, std::string key) 
{ 
    string nkey; 
    if (!key.empty()) 
    nkey = key + "."; 

    ptree::const_iterator end = pt.end(); 
    for(ptree::iterator it = pt.begin(); it != end; ++it){ 

     //if the node's id is a .html filname, save the node to file 
     string id = it->second.get("<xmlattr>.id",""); 

     if(id.find("B.html") != std::string::npos){ //Let's just test for "B.html" 
      write_xml("test.html", pt);   //saves entire tree 
      write_xml("test.html", it->second); //saves only children of the node 
     } 

     parse_tree(it->second, nkey + it->first); //recursion 
    } 
} 

結果

（我們得到整個樹，我們只希望節點）使用write_xml

<node id="A.html"> 
    <subnode> child A1 </subnode> 
    <subnode> child A2 </subnode> 
</node> 
<node id="B.html"> 
    <subnode> child B1 </subnode> 
    <subnode> child B2 </subnode> 
</node> 

結果（ 「test.html的」，它 - >第二）

（我們沒有父節點..唯一的孩子節點）

<subnode> child B1 </subnode> 
<subnode> child B2 </subnode> 

期望的結果

（我們想要的節點，它的孩子，......像這樣）

<node id="B.html"> 
    <subnode> child B1 </subnode> 
    <subnode> child B2 </subnode> 
</node> 

Answer 1

更新2

改寫響應評論/更新的問題。

有兩種方法。

1. 可以使用無證功能write_xml_element寫的單個元素（使用密鑰元素名稱）：

   // write the single element: (undocumented API) 
       boost::property_tree::xml_parser::write_xml_element(
         std::cout, it->first, it->second, 
         0, settings 
        ); 
   

2. ，或者你可以用一個孩子創建一個新的ptree對象

   ptree tmp; 
       tmp.add_child(it->first, it->second); 
       write_xml(std::cout, tmp, settings); 
   

Live On Coliru

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

#include <fstream> 
#include <iostream> 

using namespace boost::property_tree; 


void parse_tree(ptree& pt, std::string key) 
{ 
    std::string nkey; 
    auto settings = xml_parser::xml_writer_make_settings<std::string>('\t', 1); 

    if (!key.empty()) { 
     nkey = key + "."; 
    } 

    ptree::const_iterator end = pt.end(); 
    for(ptree::iterator it = pt.begin(); it != end; ++it) 
    { 
     //if the node's id an .html filname, save the node to file 
     std::string id = it->second.get("<xmlattr>.id",""); 

     if (id.find(key) != std::string::npos) { 
      // write the single element: (undocumented API) 
      boost::property_tree::xml_parser::write_xml_element(
        std::cout, it->first, it->second, 
        0, settings 
       ); 

      // or: create a new pt with the single child 
      std::cout << "\n==========================\n\n"; 
      ptree tmp; 
      tmp.add_child(it->first, it->second); 
      write_xml(std::cout, tmp, settings); 
     } 

     parse_tree(it->second, nkey + it->first); //recursion 
    } 
} 

int main() { 
    ptree pt; 
    read_xml("input.txt", pt); 

    parse_tree(pt, "B"); 
} 

輸出：

<node id="B.html"> 
    <subnode> child B1 </subnode> 
    <subnode> child B2 </subnode> 
</node> 

========================== 

<?xml version="1.0" encoding="utf-8"?> 
<node id="B.html">  
    <subnode> child B1 </subnode> 
    <subnode> child B2 </subnode> 
</node>