为用于编辑C++的.json数据指定编号

Question

我需要将用户输入编号分配给.json数据的显示部分，以便可以在后面的函数中编辑数据。

我有这样的代码：

int choice;
int numeration = 1;
for (auto& check : airports.items())   //outputs airport city and airport code numbered from 1
{
    std::cout << numeration << ". " << airports[check.key()]["city"] << " " << airports[check.key()]["shortVersion"] << std::endl;
    numeration++;
}

std::cout << "Your choice";    //user inputs the number of the displayed airport
std::cin >> choice;

这是.json文件。

{
  "(LGW)": {
     "address": "Horley, Gatwick RH6 0NP, UK",
     "city": "London",
     "shortVersion": "(LGW)"
    },
  "(RIX)": {
     "address: "Marupe, LV-1053",
     "city": "Riga",
     "shortVersion": "(RIX)"
    }
}

如何将用户输入的数字分配给显示的机场，以便程序稍后仅从所选数据中编辑变量，或者分别删除(LGW)或(RIX)之类的整个组？例如，用户输入1(用于(LGW))，然后他可以在(LGW)下编辑city、address或shortVersion变量。

Answer 1

我将机场存储在一个数组中，如下所示：

{
    "airports": [{
            "address": "Horley, Gatwick RH6 0NP, UK",
            "city": "London",
            "shortVersion": "(LGW)"
        },
        {
            "address": "Marupe, LV-1053",
            "city": "Riga",
            "shortVersion": "(RIX)"
        }
    ]
}

json中的数组是有序的，参见：json.org。然后，您将使用用户输入的索引访问所需的机场。

编辑:索引是根据机场在json数组中的顺序隐含的。"London“将是索引0，"Riga”1等等...

访问机场的代码将取决于您正在使用的json库。其伪代码如下所示：

int user_selection = 1; // Whatever number the user picked...
JsonArray airports = json["airports"];
JsonObject airport = airports[user_selection]; // Index the array based on user's input
airport["city"] = "Amsterdam"; // Change city from Riga to Amsterdam

Edit2:使用nlohmann json库：

#include "json.hpp"

#include <iostream>
#include <string>

std::string GenerateJson(const std::string& city, const std::string& address, const std::string& iata_code)
{
  json j;
  json j_array = json::array();
  json j_object = json::object();

  j_object["city"] = city;
  j_object["address"] = address;
  j_object["shortVersion"] = iata_code;
  j_array.emplace_back(j_object);
  j["airports"] = j_array;

  return j.dump(4);
}

int main()
{
  auto json = R"(
  {
      "airports": [{
              "address": "Horley, Gatwick RH6 0NP, UK",
              "city": "London",
              "shortVersion": "LGW"
          },
          {
              "address": "Marupe, LV-1053",
              "city": "Riga",
              "shortVersion": "RIX"
          }
      ]
  }
)"_json;

  int index = 1;
  auto& airports = json["airports"];
  for (const auto& airport : airports)
  {
    std::cout << index << ") " << airport["city"].get<std::string>() << " " << airport["shortVersion"].get<std::string>() << std::endl;
    ++index;
  }

  int choice = 0;
  std::cout << "Your choice:" << std::endl;
  std::cin >> choice;

  choice -= 1;

  std::string iata_code;
  std::cout << "Change IATA airport code:" << std::endl;
  std::cin >> iata_code;

  auto& airport = airports[choice];
  airport["shortVersion"] = iata_code;

  std::cout << json.dump(4) << std::endl;

  int any;
  std::cout << "Press any key to exit..." << std::endl;
  std::cin >> any;
}