Creating a JSON object from a file

To create a JSON object from the contents of a JSON file, you can use the json::parse method in combination with a file stream:

1#include <iostream>
2#include <fstream>
3#include <json.hpp>
4using json = nlohmann::json;
5
6int main() {
7  std::ifstream file("data.json");
8  json data = json::parse(file);
9
10  std::cout << data.dump(2);
11}

This code opens the file "data.json" for reading using an std::ifstream. It then passes the file stream directly to json::parse, which will read the file contents and parse it into a json object.

We can then access the data from the JSON object as normal, such as outputting it to the console using dump().

Make sure to #include <fstream> to bring in the file stream functionality.