njson

A simple representation of JSON and a JSON file parser in C++.

Example Usage

Parsing a json file:

JsonParser parser("config.json");
if (parser.has_error())
	return 1;

Json::pointer root_node = parser.parse();

Find the string key in the json node. json is a unique_ptr to an instance of the Json class with the object type (an unordered_map):

Json::pointer& string_node = json->find("string");

We can now validate the type of this node and get it's value:

if (string_node->is<std::string>())
{
	std::string& str = string_node->get<std::string>();

	// if desired we can also alter the actual string
	str += "adding more words";
}

Without the is<T>() method we can still call get<T>(), but it will throw and exception if we specify the wrong type as the template argument. This exception can of course be catch-ed and handled appropriately by the user if desired.

We can also use get<T>() on objects and arrays to get a reference to the data structure:

// Json::array is a std::vector
Json::array& server_nodes = json->find("servers")->get<Json::array>();

// And of course we can iterate and use range-based for-loops
for (Json::pointer const& n : server_nodes)
	...

Printing/outputing json is quite easy, any std::ostream will work:

// through stream operators:
std::cout << json << std::end;

// or with the print function:
json->print();

Json Node

A json node hold a value and the type of it's value. The types can be:

• null - a std::nullptr_t type node that doesn't hold a value
• object - a std::unordered_map<std::string, std::unique_ptr<Json>>
• array - a std::vector of std::unique_ptr<Json>
• string - a std::string
• double
• int
• bool