使用 nlohmann/json 序列化 c++jsonc++17序列化

原文链接
nlohmann/json JSON for Modern C++

#include #include #include #include #include "json.hpp"namespace nl = nlohmann; enum class TestEnum : int { Left = 0, Right }; struct SubTestStruct { int test = 0; }; struct TestStruct { int test = 0; bool testBool = false; TestEnum testEnum = TestEnum::Left; std::optional testOpt; std::vector testVec; SubTestStruct subTestStruct; }; // nl 不直接支持 optional，使用 adl_serializer 可以支持任意类型的序列化 // https://github.com/nlohmann/json/pull/2117 // https://github.com/nlohmann/json#how-do-i-convert-third-party-types namespace nlohmann { template struct adl_serializer> { static void to_json(json& j, const std::optional& opt) { if (opt == std::nullopt) { j = nullptr; } else { j = *opt; // this will call adl_serializer::to_json which will // find the free function to_json in T's namespace! } }static void from_json(const json& j, std::optional& opt) { if (j.is_null()) { opt = std::nullopt; } else { opt = j.get(); // same as above, but with // adl_serializer::from_json } } }; }// 序列化struct,class NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(SubTestStruct, test) NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(TestStruct, test, testBool, testEnum, testOpt, testVec, subTestStruct)// 序列化enum NLOHMANN_JSON_SERIALIZE_ENUM(TestEnum, { {TestEnum::Left, "Left"}, {TestEnum::Right, "Right"}, })void printTest(const TestStruct& s) { nl::json jsonValue; nl::to_json(jsonValue, s); std::cout << "TestStruct test: " << s.test << ", testBool: " << s.testBool << ", testEnum: " << (int) s.testEnum << ", testOpt: " << (s.testOpt.has_value() && s.testOpt.value()) << ", testVec: { "; for(auto val : s.testVec) { std::cout << val << ","; } std::cout << "\b" << " }"; std::cout << ", subTestStruct.test: " << s.subTestStruct.test; std::cout << std::endl; }int main() { // 写入 std::ofstream sf("config.json"); nl::json j; TestStruct s; s.test = 100; s.testOpt = true; for(int i = 0; i < 5; ++i) { s.testVec.push_back(i); } s.subTestStruct.test = 99; printTest(s); nl::to_json(j, s); // 单独获取一个值 std::cout << "Json value: " << j["test"] << std::endl; //写入文件 sf << j; sf.close(); //读取 std::ifstreamis("config.json"); nl::json readJson; is >> readJson; TestStruct newS = readJson.get(); //nl::from_json(readJson, newS); printTest(newS); is.close(); return 0; }

【使用 nlohmann/json 序列化】注： nl_json 是一个 utf-8 only 库，使用中文下使用需要注意编码