nlohmann json, writing to json file

To write data to a JSON file using the nlohmann json library in C++, you can follow these steps:

  1. Include the necessary headers: Begin by including the necessary headers for working with nlohmann json:
#include <iostream>
#include <fstream>
#include <nlohmann/json.hpp>

The <iostream> header is used for input/output operations, <fstream> is used for working with file streams, and <nlohmann/json.hpp> is the header file for the nlohmann json library.

  1. Create a JSON object: Next, create a JSON object using the nlohmann::json class:
nlohmann::json jsonData;

This object will hold the data that you want to write to the JSON file.

  1. Populate the JSON object: Populate the JSON object with the desired data. You can add values to the JSON object using the [] operator:
jsonData["name"] = "John Doe";
jsonData["age"] = 30;

In this example, we are adding a "name" key with the value "John Doe" and an "age" key with the value 30 to the JSON object.

  1. Open a file stream: Open a file stream to create or open the JSON file for writing:
std::ofstream file("data.json");

Here, we are opening a file stream named "file" with the filename "data.json". If the file does not exist, it will be created. If it already exists, its contents will be overwritten.

  1. Write the JSON data to the file: Use the << operator to write the JSON data to the file:
file << jsonData;

This will write the JSON data stored in the jsonData object to the file.

  1. Close the file stream: Close the file stream to release the resources:
file.close();

It is good practice to close the file stream after you have finished writing the data.

And that's it! Following these steps, you can write data to a JSON file using the nlohmann json library in C++.