Jem

Just a simple, single-header, modern C++ (17) library for parsing JSON.

Usage example

First, make sure the JSON file is correct as the library doesn't check for errors. Now here's how you can extract what you need out of this nonsense:

// comments are supported
{
  "key": null,
  "todos": [
    "do the laundry",  // <-- let's extract this
    "work"
  ],

  "pings": 32932939231212,
  "cake-left": 0.0001021212112
}

#include <iostream>
#include "Jem/jem.hpp"


int main() {
    // parse the file via the path, there is also a secondary constructor (Json(std::string)) to allow
    // feeding the JSON source string directly
    jem::Json json(std::filesystem::path("path/to/file.json"));

    auto my_json = json.dump();  // type: jem::JSON_t

    bool has_key = my_json.toObject()["key"].isNull();  // to check if the field/value is null

    // let's extract the first todo
    std::string first_todo = my_json.toObject()["todos"].toList()[0].toString();
    std::cout << first_todo << std::endl;  // output: `do the laundry`
}

Trivia

• Numbers aren't kept in their own type but rather in an std::string to prevent precision loss.
• The type jem::JSON_t returned by dump, is basically an abstraction over std::variant<std::string, bool, JSObject, JSList, std::nullptr_t>.
• The lib internally uses a recursive-descent approach for parsing.