英文:
nlohmann/json: how to convert a string to a list and iterate over this list?
问题
nlohmann/json：如何将字符串转换为列表并迭代该列表？
我在一个非常特殊的情况下，字符串中包含一个列表。请参阅下面的“Body”和“lidar_calibration”键：关联的值是嵌套在字符串“[]”中的列表。
#include <iostream>
#include <fstream>
#include <sstream>
#include <nlohmann/json.hpp>
int main() {
{
std::ifstream inp("calibration.json");
std::string out; while(inp >> out) std::cout << out; std::cout << std::endl;
}
std::cout << std::endl;
{
std::ifstream inp("calibration.json");
nlohmann::json inpJson = nlohmann::json::parse(inp);
std::cout << inpJson << std::endl;
}
std::cout << std::endl;
{
std::ifstream inp("calibration.json");
nlohmann::json inpJson = nlohmann::json::parse(inp);
std::stringstream str; str << inpJson["Body"]["lidar_calibration"];
nlohmann::json calibJson = nlohmann::json::parse(str);
std::cout << calibJson << std::endl;
}
std::cout << std::endl;
{
std::ifstream inp("calibration.json");
nlohmann::json inpJson = nlohmann::json::parse(inp);
std::stringstream str; str << inpJson["Body"]["lidar_calibration"];
nlohmann::json calibJson = nlohmann::json::parse(str);
for (auto const & calib : calibJson) std::cout << calib << std::endl;
}
}
$ g++ -I /usr/include/nlohmann -o calibration calibration.cpp
$ ./calibration
{"Head":{"ErrorCode":"0","Message":"Success"},"Body":{"lidar_calibration":"[{\"i\":1,\"e\":\"15.039\",\"a\":\"0.301\"},{\"i\":2,\"e\":\"14.025\",\"a\":\"0.313\"},{\"i\":3,\"e\":\"13.019\",\"a\":\"0.306\"},{\"i\":4,\"e\":\"12.012\",\"a\":\"0.299\"},{\"i\":5,\"e\":\"11.009\",\"a\":\"0.291\"},{\"i\":6,\"e\":\"10.005\",\"a\":\"0.292\"},{\"i\":7,\"e\":\"9.002\",\"a\":\"0.288\"},{\"i\":8,\"e\":\"8.006\",\"a\":\"0.280\"},{\"i\":9,\"e\":\"7.005\",\"a\":\"0.278\"},{\"i\":10,\"e\":\"6.007\",\"a\":\"0.282\"},{\"i\":11,\"e\":\"5.009\",\"a\":\"0.274\"},{\"i\":12,\"e\":\"4.009\",\"a\":\"0.278\"},{\"i\":13,\"e\":\"3.015\",\"a\":\"0.271\"},{\"i\":14,\"e\":\"2.021\",\"a\":\"0.271\"},{\"i\":15,\"e\":\"1.029\",\"a\":\"0.272\"},{\"i\":16,\"e\":\"0.036\",\"a\":\"0.266\"},{\"i\":17,\"e\":\"-0.957\",\"a\":\"0.262\"},{\"i\":18,\"e\":\"-1.954\",\"a\":\"0.266\"},{\"i\":19,\"e\":\"-2.949\",\"a\":\"0.260\"},{\"i\":20,\"e\":\"-3.945\",\"a\":\"0.254\"},{\"i\":21,\"e\":\"-4.940\",\"a\":\"0.245\"},{\"i\":22,\"e\":\"-5.940\",\"a\":\"0.243\"},{\"i\":23,\"e\":\"-6.937\",\"a\":\"0.243\"},{\"i\":24,\"e\":\"-7.934\",\"a\":\"0.241\"},{\"i\":25,\"e\":\"-8.936\",\"a\":\"0.232\"},{\"i\":26,\"e\":\"-9.936\",\"a\":\"0.238\"},{\"i\":27,\"e\":\"-10.940\",\"a\":\"0.236\"},{\"i\":28,\"e\":\"-11.946\",\"a\":\"0.223\"},{\"i\":29,\"e\":\"-12.950\",\"a\":\"0.215\"},{\"i\":30,\"e\":\"-13.959\",\"a\":\"0.211\"},{\"i\":31,\"e\":\"-14.974\",\"a\":\"0.207\"},{\"i\":32,\"e\":\"-15.992\",\"a\":\"0.205\"}]"}}
{"Body":{"lidar_calibration":"[{\"i\":1,\"e\":\"15.039\",\"a\":\"0.301\"},{\"i\":2,\"e\":\"14.025
<details>
<summary>英文:</summary>
nlohmann/json: how to convert a string to a list and iterate over this list?
I am in a very specific case with a list wrapped into a string. See the "Body" and "lidar_calibration" keys below: the associated value is a list embedded into a string `"[]"`.
> cat calibration.json
{
"Head": {
"ErrorCode": "0",
"Message": "Success"
},
"Body": {
"lidar_calibration": "[{"i":1,"e":"15.039","a":"0.301"},{"i":2,"e":"14.025","a":"0.313"},{"i":3,"e":"13.019","a":"0.306"},{"i":4,"e":"12.012","a":"0.299"},{"i":5,"e":"11.009","a":"0.291"},{"i":6,"e":"10.005","a":"0.292"},{"i":7,"e":"9.002","a":"0.288"},{"i":8,"e":"8.006","a":"0.280"},{"i":9,"e":"7.005","a":"0.278"},{"i":10,"e":"6.007","a":"0.282"},{"i":11,"e":"5.009","a":"0.274"},{"i":12,"e":"4.009","a":"0.278"},{"i":13,"e":"3.015","a":"0.271"},{"i":14,"e":"2.021","a":"0.271"},{"i":15,"e":"1.029","a":"0.272"},{"i":16,"e":"0.036","a":"0.266"},{"i":17,"e":"-0.957","a":"0.262"},{"i":18,"e":"-1.954","a":"0.266"},{"i":19,"e":"-2.949","a":"0.260"},{"i":20,"e":"-3.945","a":"0.254"},{"i":21,"e":"-4.940","a":"0.245"},{"i":22,"e":"-5.940","a":"0.243"},{"i":23,"e":"-6.937","a":"0.243"},{"i":24,"e":"-7.934","a":"0.241"},{"i":25,"e":"-8.936","a":"0.232"},{"i":26,"e":"-9.936","a":"0.238"},{"i":27,"e":"-10.940","a":"0.236"},{"i":28,"e":"-11.946","a":"0.223"},{"i":29,"e":"-12.950","a":"0.215"},{"i":30,"e":"-13.959","a":"0.211"},{"i":31,"e":"-14.974","a":"0.207"},{"i":32,"e":"-15.992","a":"0.205"}]"
}
}
> cat calibration.cpp
```cpp
#include <iostream>
#include <fstream>
#include <sstream>
#include <nlohmann/json.hpp>
int main() {
{
std::ifstream inp("calibration.json");
std::string out; while(inp >> out) std::cout << out; std::cout << std::endl;
}
std::cout << std::endl;
{
std::ifstream inp("calibration.json");
nlohmann::json inpJson = nlohmann::json::parse(inp);
std::cout << inpJson << std::endl;
}
std::cout << std::endl;
{
std::ifstream inp("calibration.json");
nlohmann::json inpJson = nlohmann::json::parse(inp);
std::stringstream str; str << inpJson["Body"]["lidar_calibration"];
nlohmann::json calibJson = nlohmann::json::parse(str);
std::cout << calibJson << std::endl;
}
std::cout << std::endl;
{
std::ifstream inp("calibration.json");
nlohmann::json inpJson = nlohmann::json::parse(inp);
std::stringstream str; str << inpJson["Body"]["lidar_calibration"];
nlohmann::json calibJson = nlohmann::json::parse(str);
for (auto const & calib : calibJson) std::cout << calib << std::endl;
}
}
$ g++ -I /usr/include/nlohmann -o calibration calibration.cpp
$ ./calibration
{"Head":{"ErrorCode":"0","Message":"Success"},"Body":{"lidar_calibration":"[{\"i\":1,\"e\":\"15.039\",\"a\":\"0.301\"},{\"i\":2,\"e\":\"14.025\",\"a\":\"0.313\"},{\"i\":3,\"e\":\"13.019\",\"a\":\"0.306\"},{\"i\":4,\"e\":\"12.012\",\"a\":\"0.299\"},{\"i\":5,\"e\":\"11.009\",\"a\":\"0.291\"},{\"i\":6,\"e\":\"10.005\",\"a\":\"0.292\"},{\"i\":7,\"e\":\"9.002\",\"a\":\"0.288\"},{\"i\":8,\"e\":\"8.006\",\"a\":\"0.280\"},{\"i\":9,\"e\":\"7.005\",\"a\":\"0.278\"},{\"i\":10,\"e\":\"6.007\",\"a\":\"0.282\"},{\"i\":11,\"e\":\"5.009\",\"a\":\"0.274\"},{\"i\":12,\"e\":\"4.009\",\"a\":\"0.278\"},{\"i\":13,\"e\":\"3.015\",\"a\":\"0.271\"},{\"i\":14,\"e\":\"2.021\",\"a\":\"0.271\"},{\"i\":15,\"e\":\"1.029\",\"a\":\"0.272\"},{\"i\":16,\"e\":\"0.036\",\"a\":\"0.266\"},{\"i\":17,\"e\":\"-0.957\",\"a\":\"0.262\"},{\"i\":18,\"e\":\"-1.954\",\"a\":\"0.266\"},{\"i\":19,\"e\":\"-2.949\",\"a\":\"0.260\"},{\"i\":20,\"e\":\"-3.945\",\"a\":\"0.254\"},{\"i\":21,\"e\":\"-4.940\",\"a\":\"0.245\"},{\"i\":22,\"e\":\"-5.940\",\"a\":\"0.243\"},{\"i\":23,\"e\":\"-6.937\",\"a\":\"0.243\"},{\"i\":24,\"e\":\"-7.934\",\"a\":\"0.241\"},{\"i\":25,\"e\":\"-8.936\",\"a\":\"0.232\"},{\"i\":26,\"e\":\"-9.936\",\"a\":\"0.238\"},{\"i\":27,\"e\":\"-10.940\",\"a\":\"0.236\"},{\"i\":28,\"e\":\"-11.946\",\"a\":\"0.223\"},{\"i\":29,\"e\":\"-12.950\",\"a\":\"0.215\"},{\"i\":30,\"e\":\"-13.959\",\"a\":\"0.211\"},{\"i\":31,\"e\":\"-14.974\",\"a\":\"0.207\"},{\"i\":32,\"e\":\"-15.992\",\"a\":\"0.205\"}]"}}
{"Body":{"lidar_calibration":"[{\"i\":1,\"e\":\"15.039\",\"a\":\"0.301\"},{\"i\":2,\"e\":\"14.025\",\"a\":\"0.313\"},{\"i\":3,\"e\":\"13.019\",\"a\":\"0.306\"},{\"i\":4,\"e\":\"12.012\",\"a\":\"0.299\"},{\"i\":5,\"e\":\"11.009\",\"a\":\"0.291\"},{\"i\":6,\"e\":\"10.005\",\"a\":\"0.292\"},{\"i\":7,\"e\":\"9.002\",\"a\":\"0.288\"},{\"i\":8,\"e\":\"8.006\",\"a\":\"0.280\"},{\"i\":9,\"e\":\"7.005\",\"a\":\"0.278\"},{\"i\":10,\"e\":\"6.007\",\"a\":\"0.282\"},{\"i\":11,\"e\":\"5.009\",\"a\":\"0.274\"},{\"i\":12,\"e\":\"4.009\",\"a\":\"0.278\"},{\"i\":13,\"e\":\"3.015\",\"a\":\"0.271\"},{\"i\":14,\"e\":\"2.021\",\"a\":\"0.271\"},{\"i\":15,\"e\":\"1.029\",\"a\":\"0.272\"},{\"i\":16,\"e\":\"0.036\",\"a\":\"0.266\"},{\"i\":17,\"e\":\"-0.957\",\"a\":\"0.262\"},{\"i\":18,\"e\":\"-1.954\",\"a\":\"0.266\"},{\"i\":19,\"e\":\"-2.949\",\"a\":\"0.260\"},{\"i\":20,\"e\":\"-3.945\",\"a\":\"0.254\"},{\"i\":21,\"e\":\"-4.940\",\"a\":\"0.245\"},{\"i\":22,\"e\":\"-5.940\",\"a\":\"0.243\"},{\"i\":23,\"e\":\"-6.937\",\"a\":\"0.243\"},{\"i\":24,\"e\":\"-7.934\",\"a\":\"0.241\"},{\"i\":25,\"e\":\"-8.936\",\"a\":\"0.232\"},{\"i\":26,\"e\":\"-9.936\",\"a\":\"0.238\"},{\"i\":27,\"e\":\"-10.940\",\"a\":\"0.236\"},{\"i\":28,\"e\":\"-11.946\",\"a\":\"0.223\"},{\"i\":29,\"e\":\"-12.950\",\"a\":\"0.215\"},{\"i\":30,\"e\":\"-13.959\",\"a\":\"0.211\"},{\"i\":31,\"e\":\"-14.974\",\"a\":\"0.207\"},{\"i\":32,\"e\":\"-15.992\",\"a\":\"0.205\"}]"},"Head":{"ErrorCode":"0","Message":"Success"}}
"[{\"i\":1,\"e\":\"15.039\",\"a\":\"0.301\"},{\"i\":2,\"e\":\"14.025\",\"a\":\"0.313\"},{\"i\":3,\"e\":\"13.019\",\"a\":\"0.306\"},{\"i\":4,\"e\":\"12.012\",\"a\":\"0.299\"},{\"i\":5,\"e\":\"11.009\",\"a\":\"0.291\"},{\"i\":6,\"e\":\"10.005\",\"a\":\"0.292\"},{\"i\":7,\"e\":\"9.002\",\"a\":\"0.288\"},{\"i\":8,\"e\":\"8.006\",\"a\":\"0.280\"},{\"i\":9,\"e\":\"7.005\",\"a\":\"0.278\"},{\"i\":10,\"e\":\"6.007\",\"a\":\"0.282\"},{\"i\":11,\"e\":\"5.009\",\"a\":\"0.274\"},{\"i\":12,\"e\":\"4.009\",\"a\":\"0.278\"},{\"i\":13,\"e\":\"3.015\",\"a\":\"0.271\"},{\"i\":14,\"e\":\"2.021\",\"a\":\"0.271\"},{\"i\":15,\"e\":\"1.029\",\"a\":\"0.272\"},{\"i\":16,\"e\":\"0.036\",\"a\":\"0.266\"},{\"i\":17,\"e\":\"-0.957\",\"a\":\"0.262\"},{\"i\":18,\"e\":\"-1.954\",\"a\":\"0.266\"},{\"i\":19,\"e\":\"-2.949\",\"a\":\"0.260\"},{\"i\":20,\"e\":\"-3.945\",\"a\":\"0.254\"},{\"i\":21,\"e\":\"-4.940\",\"a\":\"0.245\"},{\"i\":22,\"e\":\"-5.940\",\"a\":\"0.243\"},{\"i\":23,\"e\":\"-6.937\",\"a\":\"0.243\"},{\"i\":24,\"e\":\"-7.934\",\"a\":\"0.241\"},{\"i\":25,\"e\":\"-8.936\",\"a\":\"0.232\"},{\"i\":26,\"e\":\"-9.936\",\"a\":\"0.238\"},{\"i\":27,\"e\":\"-10.940\",\"a\":\"0.236\"},{\"i\":28,\"e\":\"-11.946\",\"a\":\"0.223\"},{\"i\":29,\"e\":\"-12.950\",\"a\":\"0.215\"},{\"i\":30,\"e\":\"-13.959\",\"a\":\"0.211\"},{\"i\":31,\"e\":\"-14.974\",\"a\":\"0.207\"},{\"i\":32,\"e\":\"-15.992\",\"a\":\"0.205\"}]"
"[{\"i\":1,\"e\":\"15.039\",\"a\":\"0.301\"},{\"i\":2,\"e\":\"14.025\",\"a\":\"0.313\"},{\"i\":3,\"e\":\"13.019\",\"a\":\"0.306\"},{\"i\":4,\"e\":\"12.012\",\"a\":\"0.299\"},{\"i\":5,\"e\":\"11.009\",\"a\":\"0.291\"},{\"i\":6,\"e\":\"10.005\",\"a\":\"0.292\"},{\"i\":7,\"e\":\"9.002\",\"a\":\"0.288\"},{\"i\":8,\"e\":\"8.006\",\"a\":\"0.280\"},{\"i\":9,\"e\":\"7.005\",\"a\":\"0.278\"},{\"i\":10,\"e\":\"6.007\",\"a\":\"0.282\"},{\"i\":11,\"e\":\"5.009\",\"a\":\"0.274\"},{\"i\":12,\"e\":\"4.009\",\"a\":\"0.278\"},{\"i\":13,\"e\":\"3.015\",\"a\":\"0.271\"},{\"i\":14,\"e\":\"2.021\",\"a\":\"0.271\"},{\"i\":15,\"e\":\"1.029\",\"a\":\"0.272\"},{\"i\":16,\"e\":\"0.036\",\"a\":\"0.266\"},{\"i\":17,\"e\":\"-0.957\",\"a\":\"0.262\"},{\"i\":18,\"e\":\"-1.954\",\"a\":\"0.266\"},{\"i\":19,\"e\":\"-2.949\",\"a\":\"0.260\"},{\"i\":20,\"e\":\"-3.945\",\"a\":\"0.254\"},{\"i\":21,\"e\":\"-4.940\",\"a\":\"0.245\"},{\"i\":22,\"e\":\"-5.940\",\"a\":\"0.243\"},{\"i\":23,\"e\":\"-6.937\",\"a\":\"0.243\"},{\"i\":24,\"e\":\"-7.934\",\"a\":\"0.241\"},{\"i\":25,\"e\":\"-8.936\",\"a\":\"0.232\"},{\"i\":26,\"e\":\"-9.936\",\"a\":\"0.238\"},{\"i\":27,\"e\":\"-10.940\",\"a\":\"0.236\"},{\"i\":28,\"e\":\"-11.946\",\"a\":\"0.223\"},{\"i\":29,\"e\":\"-12.950\",\"a\":\"0.215\"},{\"i\":30,\"e\":\"-13.959\",\"a\":\"0.211\"},{\"i\":31,\"e\":\"-14.974\",\"a\":\"0.207\"},{\"i\":32,\"e\":\"-15.992\",\"a\":\"0.205\"}]"
How can I iterate over this list?
答案1
得分: 2
将其转换为字符串，而不是使用operator<<将其序列化为另一个JSON。
英文:
Just:
std::string str = inpJson["Body"]["lidar_calibration"];
nlohmann::json calibJson = nlohmann::json::parse(str);
Convert it to string instead of serializing with operator<< to another json.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论