1// ----------------------------------------------------------------------------
2// Copyright (C) 2002-2006 Marcin Kalicinski
3//
4// Distributed under the Boost Software License, Version 1.0.
5// (See accompanying file LICENSE_1_0.txt or copy at
6// http://www.boost.org/LICENSE_1_0.txt)
7//
8// For more information, see www.boost.org
9// ----------------------------------------------------------------------------
10
11#include <boost/property_tree/ptree.hpp>
12#include <boost/property_tree/info_parser.hpp>
13#include <iostream>
14#include <iomanip>
15#include <string>
16
17using namespace boost::property_tree;
18
19 static ptree dflt;
20
21 // Process settings using empty ptree trick. Note that it is considerably simpler
22// than version which does not use the "trick"
23void process_settings(const std::string &filename)
24{
25 ptree pt;
26 read_info(filename, pt);
27 const ptree &settings = pt.get_child(path: "settings", default_value&: dflt);
28 std::cout << "\n Processing " << filename << std::endl;
29 std::cout << " Setting 1 is " << settings.get(path: "setting1", default_value: 0) << std::endl;
30 std::cout << " Setting 2 is " << settings.get(path: "setting2", default_value: 0.0) << std::endl;
31 std::cout << " Setting 3 is " << settings.get(path: "setting3", default_value: "default") << std::endl;
32}
33
34// Process settings not using empty ptree trick. This one must duplicate much of the code.
35void process_settings_without_trick(const std::string &filename)
36{
37 ptree pt;
38 read_info(filename, pt);
39 if (boost::optional<ptree &> settings = pt.get_child_optional(path: "settings"))
40 {
41 std::cout << "\n Processing " << filename << std::endl;
42 std::cout << " Setting 1 is " << settings.get().get(path: "setting1", default_value: 0) << std::endl;
43 std::cout << " Setting 2 is " << settings.get().get(path: "setting2", default_value: 0.0) << std::endl;
44 std::cout << " Setting 3 is " << settings.get().get(path: "setting3", default_value: "default") << std::endl;
45 }
46 else
47 {
48 std::cout << "\n Processing " << filename << std::endl;
49 std::cout << " Setting 1 is " << 0 << std::endl;
50 std::cout << " Setting 2 is " << 0.0 << std::endl;
51 std::cout << " Setting 3 is " << "default" << std::endl;
52 }
53}
54
55int main()
56{
57 try
58 {
59 std::cout << "Processing settings with empty-ptree-trick:\n";
60 process_settings(filename: "settings_fully-existent.info");
61 process_settings(filename: "settings_partially-existent.info");
62 process_settings(filename: "settings_non-existent.info");
63 std::cout << "\nProcessing settings without empty-ptree-trick:\n";
64 process_settings_without_trick(filename: "settings_fully-existent.info");
65 process_settings_without_trick(filename: "settings_partially-existent.info");
66 process_settings_without_trick(filename: "settings_non-existent.info");
67 }
68 catch (std::exception &e)
69 {
70 std::cout << "Error: " << e.what() << "\n";
71 }
72 return 0;
73}
74

source code of boost/libs/property_tree/examples/empty_ptree_trick.cpp