nlohmann::json的使用非常简单，只需要包含.hpp文件即可，这是它的官网https://github.com/nlohmann/json
简单使用：

#include "json.hpp"
#include <iostream>

using Info = nlohmann::json;

int main()
{
	Info info;
	std::cout << info.size() << std::endl;
	info["a"] = "b";

	std::cout << info["a"] << std::endl;

	auto iter = info.find("a");
	if (iter == info.end()) {
		std::cout << "not found" << std::endl;
	}
	else {
		std::cout << *iter << std::endl;
	}

	std::string s = R"({
		"name" : "nick",
		"credits" : "123",
		"ranking" : 1
	})";

	auto j = nlohmann::json::parse(s);
	std::cout << j["name"] << std::endl;

	std::string ss = j.dump();
	std::cout << "ss : " << ss << std::endl;

	Info j1;
	Info j2 = nlohmann::json::object();
	Info j3 = nlohmann::json::array();

	std::cout << j1.is_object() << std::endl;
	std::cout << j1.type_name() << std::endl;

	std::cout << j2.is_object() << std::endl;
	std::cout << j2.is_array() << std::endl;

	Info infoo{
		{"name", "darren"},
		{"credits", 123},
		{"ranking", 1}
	};

	std::cout << infoo["name"] << std::endl;

	std::cout << infoo.type_name() << std::endl;

	//遍历
	for (auto iter = infoo.begin(); iter != infoo.end(); iter++) {
		std::cout << iter.key() << " : " << iter.value() << std::endl;
		//std::cout << iter.value() << std::endl;
		//std::cout << *iter << std::endl;
	}

	system("pause");
	return 0;
}

输出：