How to Convert a JSON String to a Map in C++ - Step by Step Examples

How to Convert a JSON String to a Map in C++ ?

Answer

To convert a JSON string to a map in C++, you can use the nlohmann::json library, which provides easy-to-use methods for parsing JSON data and converting it into various data structures, including std::map.

✐ Examples

1 Converting a JSON String to a Map

We can convert a JSON string to a map in C++ by using the nlohmann::json library to parse the JSON string and then iterating over the parsed JSON object to populate the map.

For example,

We start by including the necessary headers: #include <iostream>, #include <map>, and #include <nlohmann/json.hpp>.
We define a JSON string containing key-value pairs.
We parse the JSON string into a nlohmann::json object.
We declare an empty std::map to store the key-value pairs.
We iterate over the JSON object and add each key-value pair to the map.
We print the resulting map to the console to verify the conversion.

C++ Program

#include <iostream>
#include <map>
#include <nlohmann/json.hpp>

int main() {
    // Define a JSON string
    std::string jsonString = R"({"1": 10, "2": 20, "3": 30, "4": 40, "5": 50})";

    // Parse the JSON string into a nlohmann::json object
    nlohmann::json jsonObject = nlohmann::json::parse(jsonString);

    // Declare an empty map to store the key-value pairs
    std::map<int, int> myMap;

    // Iterate over the JSON object and add each key-value pair to the map
    for (auto it = jsonObject.begin(); it != jsonObject.end(); ++it) {
        myMap[std::stoi(it.key())] = it.value();
    }

    // Print the resulting map
    std::cout << "Map from JSON string:" << std::endl;
    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Output

Map from JSON string:
1: 10
2: 20
3: 30
4: 40
5: 50

Summary

In this tutorial, we learned How to Convert a JSON String to a Map in C++ language with well detailed examples.

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How to Convert a JSON String to a Map in C++ - Step by Step Examples