nlohmann json

JSON for Modern C++

https://github.com/nlohmann/json

解析复杂结构，不好意忘了贴具体的json数据了，大家看解析过程应该可以猜到。

#include <nlohmann/json.hpp>

// for convenience
using json = nlohmann::json;
std::string media_config_string = std::string(*json_param);
    json media_config = json::parse(media_config_string);

    std::vector<erizo::RtpMap> rtp_mappings;
    if (media_config.find("rtpMappings") != media_config.end()) {
      json rtp_map_json = media_config["rtpMappings"];
      for (json::iterator it = rtp_map_json.begin(); it != rtp_map_json.end(); ++it) {
        erizo::RtpMap rtp_map;
        if (it.value()["payloadType"].is_number()) {
          rtp_map.payload_type = it.value()["payloadType"];
        } else {
          continue;
        }
        if (it.value()["encodingName"].is_string()) {
          rtp_map.encoding_name = it.value()["encodingName"];
        } else {
          continue;
        }
        if (it.value()["mediaType"].is_string()) {
          if (it.value()["mediaType"] == "video") {
            rtp_map.media_type = erizo::VIDEO_TYPE;
          } else if (it.value()["mediaType"] == "audio") {
            rtp_map.media_type = erizo::AUDIO_TYPE;
          } else {
            continue;
          }
        } else {
          continue;
        }
        if (it.value()["clockRate"].is_number()) {
          rtp_map.clock_rate = it.value()["clockRate"];
        }
        if (rtp_map.media_type == erizo::AUDIO_TYPE) {
          if (it.value()["channels"].is_number()) {
            rtp_map.channels = it.value()["channels"];
          }
        }
        if (it.value()["formatParameters"].is_object()) {
          json format_params_json = it.value()["formatParameters"];
          for (json::iterator params_it = format_params_json.begin();
              params_it != format_params_json.end(); ++params_it) {
            std::string value = params_it.value();
            std::string key = params_it.key();
            rtp_map.format_parameters.insert(rtp_map.format_parameters.begin(),
                std::pair<std::string, std::string> (key, value));
          }
        }
        if (it.value()["feedbackTypes"].is_array()) {
          json feedback_types_json = it.value()["feedbackTypes"];
          for (json::iterator feedback_it = feedback_types_json.begin();
              feedback_it != feedback_types_json.end(); ++feedback_it) {
              rtp_map.feedback_types.push_back(*feedback_it);
          }
        }
        rtp_mappings.push_back(rtp_map);
      }
    }