JSON support, is spotty with boost property tree. The property tree dataset is not typed, and does not support arrays as such. Thus, the following JSON / property tree mapping is used: JSON objects are mapped to nodes. Each property is a child node. JSON arrays are mapped to nodes. Each element is a child … Read more
The property tree iterators point to pairs of the form (key, tree) of type ptree::value_type. The standard loop for iterating through the children of the node at path therefore looks like: BOOST_FOREACH(const ptree::value_type &v, pt.get_child(path)) { // v.first is the name of the child. // v.second is the child tree. }
The solution was to add the trim_whitespace flag to the call to read_xml: #include <boost/property_tree/ptree.hpp> #include <boost/property_tree/xml_parser.hpp> int main( void ) { // Create an empty property tree object using boost::property_tree::ptree; ptree pt; // reading file.xml read_xml(“file.xml”, pt, boost::property_tree::xml_parser::trim_whitespace ); // writing the unchanged ptree in file2.xml boost::property_tree::xml_writer_settings<char> settings(‘\t’, 1); write_xml(“file2.xml”, pt, std::locale(), settings); return … Read more
optional< const ptree& > child = node.get_child_optional( “possibly_missing_node” ); if( !child ) { // child node is missing }
Ok, I’ve solved it like this, (of course it won’t suite for everybody, as it is a bit of a hack, that need further work). I’ve wrote my own write_json function (simply copied the files, json_parser.hpp and json_parser_write.hpp to my project) and modified the following lines in json_parser_write.hpp: commented line 37 – escaping the quote … Read more
Note that property_tree interprets the keys as paths, e.g. putting the pair “a.b”=”z” will create an {“a”:{“b”:”z”}} JSON, not an {“a.b”:”z”}. Otherwise, using property_tree is trivial. Here is a little example. #include <sstream> #include <map> #include <boost/property_tree/ptree.hpp> #include <boost/property_tree/json_parser.hpp> using boost::property_tree::ptree; using boost::property_tree::read_json; using boost::property_tree::write_json; void example() { // Write json. ptree pt; pt.put (“foo”, … Read more
Simple Array: #include <boost/property_tree/ptree.hpp> using boost::property_tree::ptree; ptree pt; ptree children; ptree child1, child2, child3; child1.put(“”, 1); child2.put(“”, 2); child3.put(“”, 3); children.push_back(std::make_pair(“”, child1)); children.push_back(std::make_pair(“”, child2)); children.push_back(std::make_pair(“”, child3)); pt.add_child(“MyArray”, children); write_json(“test1.json”, pt); results in: { “MyArray”: [ “1”, “2”, “3” ] } Array over Objects: ptree pt; ptree children; ptree child1, child2, child3; child1.put(“childkeyA”, 1); child1.put(“childkeyB”, 2); … Read more