C++产品开发讲座-(三)常⽤组件1-应⽤配置

C++产品开发讲座-(三)常⽤组件1-应⽤配置

应⽤参数较多，往往需⽤⼀个或多个配置文件进⾏储存
配置文件的保存与读取⽅法，尽可能简单
避免逐参数赋值，参数多了，发⽣了版本升级，功能修改
往往容易造成修改遗漏使得配置文件对不上

不好的例子1

bool readDotCfg(ParamDot& param)
{
    
    
 std::string file_cfg = "./config/dot.cfg";
 std::string line;
 std::ifstream ifile(file_cfg, std::ios::in);
 if (!ifile)
 {
    
    
	 qDebug() << "file not found:" << file_cfg.c_str();
	 return false;
 }
 while (std::getline(ifile, line))
 {
    
    
	 std::string key;
	 std::string val;
	 if (!parseKeyVal(line, key, val)) continue;
	 //std::cout << key << ":" << val << std::endl;
	 if (key == "positive") param.positive = std::atoi(val.c_str());
	 if (key == "height0") param.height0 = std::atof(val.c_str());
	 if (key == "height0_row") param.height0_row = std::atof(val.c_str());
	 if (key == "stagger0_col") param.stagger0_col = std::atof(val.c_str());
	 if (key == "p2r_stagger") param.p2r_stagger = std::atof(val.c_str());
	 if (key == "p2r_height") param.p2r_height = std::atof(val.c_str());
	 if (key == "row_s") param.row_s = std::atoi(val.c_str());
	 if (key == "row_e") param.row_e = std::atoi(val.c_str());
	 if (key == "col_s") param.col_s = std::atoi(val.c_str());
	 if (key == "col_e") param.col_e = std::atoi(val.c_str());
	 if (key == "th_gray_min") param.th_gray_min =
	(uint8_t)std::atoi(val.c_str());
 }
 param.printInfo();
 return true;
}

不好的例子2

bool Params::load(const std::string &file_config)
{
    
    
 	 QFile qfile(QString::fromStdString(file_config));
	 if (!qfile.exists())
	 {
    
    
		 dh_url = "rtsp://admin:[email protected]:554/cam/realmonitor?
		 channel=1&subtype=0";
		 save_dh = true;
		 arcing_port = "COM1";
		 th_arcing = 0;
		 default_height = 0;
		 default_stagger = 0;
		 th_stagger_min = -400;
		 th_stagger_max = 400;
		 th_height_min = 6000;
		 th_height_max = 4000;
		 QJsonObject jobj_root;
		 // app
		 QJsonObject jobj;
		 jobj.insert("dh_url", dh_url.c_str());
		 jobj.insert("flag_record_dh", save_dh);
		 jobj.insert("arcing_port", arcing_port.c_str());
		 jobj.insert("th_arcing", th_arcing);
		 jobj.insert("default_height", default_height);
		 jobj.insert("default_stagger", default_stagger);
		 jobj.insert("th_stagger_min", th_stagger_min);
		 jobj.insert("th_stagger_max", th_stagger_max);
		 jobj.insert("th_height_min", th_height_min);
		 jobj.insert("th_height_max", th_height_max);
		 jobj_root.insert("app", jobj);
		 QJsonDocument jdoc;
		 jdoc.setObject(jobj_root);
		 QByteArray bytes = jdoc.toJson(QJsonDocument::Indented);
		 if (!qfile.open(QIODevice::WriteOnly | QIODevice::Text))
		 {
    
    
		 	return false;
		 }
		 qfile.write(bytes);
		 qfile.close();
	 }
	 else
	 {
    
    
		 qfile.open(QIODevice::ReadOnly | QIODevice::Text);
		 QByteArray bytes = qfile.readAll();
		 QJsonDocument jdoc = QJsonDocument::fromJson(bytes);
		 if (!jdoc.isObject())
		 {
    
    
		 	return false;
		 }
		 QJsonObject obj_root = jdoc.object();
		 if (obj_root.empty())
		 {
    
    
		 	return false;
		 }
		 QJsonObject obj = obj_root.take("app").toObject();
		 dh_url = obj.take("dh_url").toString().toStdString();
		 save_dh = obj.take("save_dh").toBool();
		 arcing_port = obj.take("arcing_port").toString().toStdString();
		 th_arcing = obj.take("th_arcing").toInt();
		 default_height = obj.take("default_height").toDouble();
		 default_height = obj.take("default_height").toDouble();
		 default_stagger = obj.take("default_stagger").toDouble();
		 th_stagger_min = obj.take("th_stagger_min").toDouble();
		 th_stagger_max = obj.take("th_stagger_max").toDouble();
		 th_height_min = obj.take("th_height_min").toDouble();
		 th_height_max = obj.take("th_height_max").toDouble();
	}
	printData();
	return true;
}

好的例子

//类定义
struct Demo
{
    
    
	uint32_t val_int = 1;
	float val_float = 9.9;
	std::string val_str = "test";
	std::array<std::string, 3> arr_str = {
    
    "str1", "str2", "str3"};
	NLOHMANN_DEFINE_TYPE_INTRUSIVE(Demo, val_int, val_float, val_str, arr_str)//
	//通过宏，避免了逐个变量⼿写赋值代码
};
// 以下封装模板函数，不论什么class，具有宏NLOHMANN_DEFINE_TYPE_INTRUSIVE都可以⽤
template <class T> 
void printObject(T&& obj)
{
    
    
	nlohmann::json json_disp;
	nlohmann::to_json(json_disp, obj);
	printf("Data: %s\n", json_disp.dump(4).c_str());
}
template <class T> 
bool loadJsonFileToObject(const std::string& file_json, T&& obj)
{
    
    
	std::ifstream ifile(file_json);
	if (!ifile.good()) return false;
	try
	{
    
     
		nlohmann::json json_obj;
		ifile >> json_obj;
		nlohmann::from_json(json_obj, obj);
	}
	catch(const std::exception& e)
	{
    
    
		printf("load failed: %s\n", e.what());
		return false;
	}
	printf("load done, ");
	print(obj);
	return true;
}
template <class T> 
bool saveObjectToJsonFile(const std::string& file_json, T&& obj)
{
    
    
	std::ofstream ofile(file_json);
	if (!ofile.good()) return false;
	nlohmann::json json_obj;
	nlohmann::to_json(json_obj, obj);
	ofile << json_obj.dump(4) << std::endl;
	return true;
}
// 读写json配置文件
Demo data;
std::cout << loadJsonFileToObject("./demo.json", data) << std::endl;
std::cout << saveObjectToJsonFile("./dump.json", data) << std::endl;