[Boost-users] An example: how I learned to iterate through property trees (ptree)

21 Jun 2013


      I just wanted to post a program I wrote that creates a boost::ptree, saves it to JSON, reads it back, then iterates through the tree and prints its nodes.  


#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <string>
#include <iostream>
using namespace std; 
using boost::property_tree::ptree; 

string indent(int level) {
  string s; 
  for (int i=0; i<level; i++) s += "  ";
  return s; 
} 

void printTree (ptree &pt, int level) {
  if (pt.empty()) {
    cerr << "\""<< pt.data()<< "\"";
  } else {
    if (level) cerr << endl; 
    cerr << indent(level) << "{" << endl;     
    for (ptree::iterator pos = pt.begin(); pos != pt.end();) {
      cerr << indent(level+1) << "\"" << pos->first << "\": "; 
      printTree(pos->second, level + 1); 
      ++pos; 
      if (pos != pt.end()) {
        cerr << ","; 
      }
      cerr << endl;
    } 
    cerr << indent(level) << " }";     
  }
  return; 
}

int main(int, char*[]) {
  // first, make a json file:
  string tagfile = "testing2.pt"; 
  ptree pt1;
  pt1.put("object1.type","ASCII");  
  pt1.put("object2.type","INT64");  
  pt1.put("object3.type","DOUBLE");  
  pt1.put("object1.value","one");  
  pt1.put("object2.value","2");  
  pt1.put("object3.value","3.0"); 
  pt1.put("object4.type", "ASCII");
  pt1.put("object4.value", "shallow");
  pt1.put("object4.subobject1.type", "ASCII");
  pt1.put("object4.subobject1.value", "deep child");
  pt1.put("object4.subobject1.subsubobject.type", "ASCII");
  pt1.put("object4.subobject1.subsubobject.value", "deep child");
  pt1.put("object5.type", "ASCII");
  pt1.put("object5.value", "shallow");
  write_json(tagfile, pt1); 

  ptree pt;
  bool success = true; 
  //try {
  read_json(tagfile, pt); 
  printTree(pt, 0); 
  cerr << endl; 
  return success; 
}


PROGRAM OUTPUT: 
rcook@rzbeast (blockbuster): ./ptree 
{
  "object1": 
  {
    "type": "ASCII",
    "value": "one"
   },
  "object2": 
  {
    "type": "INT64",
    "value": "2"
   },
  "object3": 
  {
    "type": "DOUBLE",
    "value": "3.0"
   },
  "object4": 
  {
    "type": "ASCII",
    "value": "shallow",
    "subobject1": 
    {
      "type": "ASCII",
      "value": "deep child",
      "subsubobject": 
      {
        "type": "ASCII",
        "value": "deep child"
       }
     }
   },
  "object5": 
  {
    "type": "ASCII",
    "value": "shallow"
   }
 }


-- 
✐Richard Cook   
✇ Lawrence Livermore National Laboratory
Bldg-453 Rm-4024, Mail Stop L-557        
7000 East Avenue,  Livermore, CA, 94550, USA
☎ (office) (925) 423-9605    
☎ (fax) (925) 423-6961
---
Information Management & Graphics Grp., Services & Development Div., Integrated Computing & Communications Dept.
(opinions expressed herein are mine and not those of LLNL)

[Boost-users] An example: how I learned to iterate through property trees (ptree)

Cook, Rich