Install and beginning - GitMasterNikanjam/nlohmann_json_examples GitHub Wiki

Since nlohmann/json is header-only, you can simply download the header file from the GitHub repository:

1. Download the header file from the latest release.

   • Link: nlohmann/json GitHub Releases

2. Include the header file in your project. Copy it to your include directory or any relevant directory in your project.

#include <nlohmann/json.hpp>

You can now use nlohmann::json as a type in your code. It's typically aliased as json for easier use:

using json = nlohmann::json;

Here is a full example showing how to use the library in a C++ program:

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

using json = nlohmann::json;

int main() {
    // Create a JSON object
    json j;
    j["name"] = "Alice";
    j["age"] = 25;
    j["is_student"] = true;
    j["skills"] = {"C++", "Python", "JavaScript"};

    // Serialize JSON to string
    std::string jsonString = j.dump();
    std::cout << "Serialized JSON: " << jsonString << std::endl;

    // Parse JSON from string
    json parsed = json::parse(jsonString);
    std::cout << "Name: " << parsed["name"] << std::endl;
    std::cout << "Age: " << parsed["age"] << std::endl;

    return 0;
}

You can compile this program using any C++ compiler. For example, using g++:

g++ -std=c++11 -o my_program main.cpp

In the nlohmann/json GitHub releases, you'll find various files such as source code archives, binaries, and sometimes other assets. However, since nlohmann/json is a header-only library, you only need the header file to use the library in your C++ program. Below are the steps to find and download the right file.

1. Go to the GitHub Release Page:

   • nlohmann/json GitHub Releases

2. Download the Correct Archive:

   • Look for a file named json.hpp, which is the main header file you need.
   • Alternatively, download the single-header file archive. Usually, it’s a file like json.hpp or inside an archive (e.g., .zip or .tar.gz) with the following format:
     • json-<version>.single-header.hpp (e.g., json-v3.11.2.single-header.hpp)
     • You can extract this and use it in your project.

   Here’s what you should look for:

   • json.hpp (the header-only file).

3. Where to Put the File in Your Project:

   • After downloading, extract the .hpp file (if it's in a compressed archive).
   • Place this file in an appropriate directory within your project, usually in an include or libs folder, or in the same directory as your source files.

/my_project
  /include
    json.hpp    # The nlohmann/json header
  /src
    main.cpp    # Your C++ source file
  CMakeLists.txt # If using CMake

In your C++ program, you simply include this header file:

#include "json.hpp"  // Assuming the file is in the same folder or in include path

using json = nlohmann::json;

int main() {
    json j = {{"name", "Alice"}, {"age", 25}, {"is_student", true}};
    std::cout << j.dump(4) << std::endl;
    return 0;
}

• Download the single-header file (typically named json.hpp or found within a .zip/.tar.gz archive).
• Place the header file in your project and include it in your C++ code.

That’s all you need to use nlohmann/json! No need for complicated installations or multiple files—just this single header will get you started.