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：
最近发现了一个问题，就是它默认会对键进行排序，那如果不想让它排序怎么办？
可以看一下官网的文档
可以看到这里说的很详细，这里提供两种方法：
std::vector<std::pair<std::string, int>> keyValuePairs; keyValuePairs.emplace_back("key3", 3); keyValuePairs.emplace_back("key1", 1); keyValuePairs.emplace_back("key2", 2); nlohmann::json jsonObject(keyValuePairs); // 输出序列化后的JSON数据 std::cout << jsonObject.dump() << std::endl; std::cout << "===============" << std::endl; nlohmann::ordered_json orderjson; orderjson["a"] = 1; orderjson["c"] = 2; orderjson["b"] = 3; std::cout << orderjson.dump(2) << std::endl;
