From ed38fcee733483d0760b39c9615c6301d2949894 Mon Sep 17 00:00:00 2001 From: Ziyu Date: Thu, 15 May 2025 19:22:50 +0800 Subject: [PATCH] =?UTF-8?q?nlohmann=5Fjson=E4=BD=BF=E7=94=A8=E6=96=B9?= =?UTF-8?q?=E6=B3=95?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- assets/save_json.json | 46 ++++++++++++++ main.cpp | 139 ++++++++++++++++++++++++++++++++++++++---- 2 files changed, 174 insertions(+), 11 deletions(-) create mode 100644 assets/save_json.json diff --git a/assets/save_json.json b/assets/save_json.json new file mode 100644 index 0000000..9119888 --- /dev/null +++ b/assets/save_json.json @@ -0,0 +1,46 @@ +{ + "name": "张三 (Zhang San)", + "age": 30, + "height_meters": 1.75, + "isStudent": false, + "email": "zhangsan@example.com", + "middleName": null, + "address": { + "street": "人民路123号 (Renmin Road No. 123)", + "city": "示例市 (Sample City)", + "zipCode": "100000", + "isPrimary": true + }, + "hobbies": [ + "编程 (Programming)", + "阅读 (Reading)", + "旅行 (Traveling)" + ], + "scores": [ + 95, + 88, + 72.5 + ], + "projects": [ + { + "projectName": "项目Alpha (Project Alpha)", + "status": "已完成 (Completed)", + "budget": 50000.75, + "isActive": true + }, + { + "projectName": "项目Beta (Project Beta)", + "status": "进行中 (In Progress)", + "budget": 120000, + "isActive": true, + "deadline": null + } + ], + "metadata": { + "version": 1.2, + "tags": [ + "data", + "example" + ] + } +} \ No newline at end of file diff --git a/main.cpp b/main.cpp index 221240f..bb4b970 100644 --- a/main.cpp +++ b/main.cpp @@ -6,21 +6,138 @@ #include #include #include +#include int main(int, char**) { - // 设置日志等级，不设置的话默认为 info - spdlog::set_level(spdlog::level::err); + try { + // 1. 载入JSON文件 + std::ifstream input_file("assets/json_example.json"); + nlohmann::ordered_json json_data = nlohmann::ordered_json::parse(input_file); + input_file.close(); + spdlog::info("JSON 成功载入!"); - // 不同等级的log - spdlog::trace("最低级别log!"); - spdlog::debug("调试信息!"); - spdlog::info("你好，世界!"); - spdlog::warn("警告!，很可能会出错"); - spdlog::error("程序出错啦!"); - spdlog::critical("最高级别的log!, 比error还严重!"); + // 2. 获取不同类型的数据 + // 2.1 字符串 (String) + std::string name = json_data["name"].get(); + spdlog::info("Name: {}", name); + + // 2.2 数字 (Number) + int age = json_data["age"].get(); + double height = json_data["height_meters"].get(); + spdlog::info("Age: {}, Height: {}", age, height); + + // 2.3 布尔值 (Boolean) + bool isStudent = json_data["isStudent"].get(); + spdlog::info("Is Student: {}", isStudent); + // 2.4 null 值 + // 检查是否为null + if (json_data["middleName"].is_null()) { + spdlog::info("Middle Name: null"); + } else { + spdlog::info("Middle Name: {}", json_data["middleName"].get()); + } + + // 2.5 另外一种方法：使用 .at() 方法访问 + std::string email = json_data.at("email").get(); + spdlog::info("Email: {}", email); + + // 3 安全访问的方法 + // 3.1 .contains() 检查某个键是否存在，如果不存在则返回 false + if (json_data.contains("email")) + { + std::string email = json_data.at("email").get(); + spdlog::info("Email: {}", email); + } + if (json_data.contains("nonExistentKey")) + { + spdlog::info("nonExistentKey found!"); // 不会执行 + } + else + { + spdlog::info("'nonExistentKey' not found."); + } + + // 3.2 .value() 获取一个可能存在的键，如果不存在则返回指定默认值（第二个参数） + std::string optional_value = json_data.value("optionalKey", "default_string_value"); + int optional_int = json_data.value("optionalNumber", 42); + spdlog::info("Optional Key (string): {}", optional_value); + spdlog::info("Optional Key (int): {}", optional_int); + + // 4 对象 (Object) + nlohmann::ordered_json address_obj = json_data["address"]; + std::string street = address_obj["street"].get(); + std::string city = address_obj.value("city", "Unknown City"); // 使用 .value() 提供默认值 + bool isPrimaryAddr = address_obj.value("isPrimary", false); // 访问对象内的布尔值 + spdlog::info("Address: {}, {}", street, city); + spdlog::info("Is Primary Address: {}", isPrimaryAddr); + + // 5.1 数组 (Array) - 字符串数组 + spdlog::info("Hobbies:"); + nlohmann::ordered_json hobbies_array = json_data["hobbies"]; + for (const auto &hobby : hobbies_array) + { + spdlog::info(" - {}", hobby.get()); + } + + // 5.2 数组 (Array) - 数字数组 + spdlog::info("Scores:"); + for (const auto &score_item : json_data["scores"]) + { + if (score_item.is_number_integer()) + { + spdlog::info(" - {} (integer)", score_item.get()); + } + else if (score_item.is_number_float()) + { + spdlog::info(" - {} (float)", score_item.get()); + } + } + + // 5.3 数组 (Array) - 对象数组 + spdlog::info("Projects:"); + nlohmann::ordered_json projects_array = json_data["projects"]; + for (const auto &project : projects_array) + { + std::string projectName = project["projectName"].get(); + std::string status = project["status"].get(); + double budget = project.value("budget", 0.0); // 使用 value 获取，若不存在则为0.0 + bool isActive = project.value("isActive", false); + + spdlog::info(" ProjectName: {}", projectName); + spdlog::info(" Status: {}", status); + spdlog::info(" Budget: {}", budget); + spdlog::info(" Is Active: {}", isActive); + if (project.contains("deadline") && project["deadline"].is_null()) + { + spdlog::info(" Deadline: null"); + } + else if (project.contains("deadline")) + { + spdlog::info(" Deadline: {}", project["deadline"].get()); + } + spdlog::info("--------------------------------"); + } + // 5.4 直接访问更深层嵌套的对象和数组 + double metadata_version = json_data["metadata"]["version"].get(); + spdlog::info("Metadata Version: {}", metadata_version); + spdlog::info("Metadata Tags:"); + for (const auto &tag_json : json_data["metadata"]["tags"]) + { + std::string tag = tag_json.get(); + spdlog::info(" - {}", tag); + } + + // 6 将json数据保存为文件 + std::ofstream output_file("assets/save_json.json"); + output_file << json_data.dump(4); // 使用 dump(4) 进行格式化输出，缩进为4个空格 + output_file.close(); + spdlog::info("JSON 数据已保存到文件 assets/save_json.json"); + + } catch (const std::exception &e) { + spdlog::error("Exception: {}", e.what()); + // return EXIT_FAILURE; + } - // 格式化输出 - spdlog::info("日志格式化输出: {} {} {}", 1, "hello", 3.14); return 0; } \ No newline at end of file