config-loader is a static reflection framework written in C++17 from parse configuration file to native data structure. It has the following characteristics:

• Simple interface, users need to define data structure and provide corresponding configuration file, the framework uses meta-programming technology to generate load interface
• The design conforms to the opening and closing principle, extends the data structure without modifying the framework
• Currently supports XML, JSON and YAML format configuration files, a variety of methods can be flexibly composed
• Lightweight, easy to integrate, less than ~1000 lines of code
• Support nested data structure, STL container
• Complete test cases
• Support from native data structure to config file, stringify data structure

Future plans:

• Provide additional C++20 version

Build

$ git clone --recursive https://github.com/netcan/config-loader.git $ cd config-loader $ mkdir build $ cd build $ cmake .. $ make -j

Run

$ cd bin/ $ ./config_loader_test

Firstly use DEFINE_SCHEMA macro to define the data structure:

// define and reflect a struct DEFINE_SCHEMA(Point, // struct Point { (double) x, // double x; (double) y); // double y; // }; // vector and string DEFINE_SCHEMA(SomeOfPoints, // struct SomeOfPoints { (std::string) name, // std::string name; (std::vector<Point>) points); // std::vector<Point> points; // };

Provide configuration files, using loadXML2Obj/loadJSON2Obj/loadYAML2Obj interfaces:

SomeOfPoints someOfPoints; auto res = loadJSON2Obj(someOfPoints, [] { return R"(  {  "name": "Some of points",  "points":[  { "x": 1.2, "y": 3.4 },  { "x": 5.6, "y": 7.8 },  { "x": 2.2, "y": 3.3 }  ]  }  )"; }); REQUIRE(res == Result::SUCCESS); REQUIRE_THAT(someOfPoints.name, Equals("Some of points")); REQUIRE(someOfPoints.points.size() == 3);

Or, through an XML configuration file.

SomeOfPoints someOfPoints; auto res = loadXML2Obj(someOfPoints, "configs/xml/SomeOfPoints.xml"); REQUIRE(res == Result::SUCCESS); REQUIRE_THAT(someOfPoints.name, Equals("Some of points")); REQUIRE(someOfPoints.points.size() == 3);

Through a YAML configuration file.

SomeOfPoints someOfPoints; auto res = loadYAML2Obj(someOfPoints, [] { return R"(  name: Some of points  points:  - x: 1.2  y: 3.4  - x: 5.6  y: 7.8  - x: 2.2  y: 3.3  )"; }); REQUIRE(res == Result::SUCCESS); REQUIRE_THAT(someOfPoints.name, Equals("Some of points")); REQUIRE(someOfPoints.points.size() == 3);

The current framework depends on the following libraries:

• tinyxml2, used for parsing xml configuration files
• jsoncpp, used for parsing json configuration files
• yamlcpp, used for parsing yaml configuration files

In the future, these libraries may be enabled through CMake options to avoid unnecessary dependencies in actual use: only using xml will only rely on the xml parsing library.

This framework requires configuration files to be provided in a standardized format. Taking XML as an example, the field name is required to correspond to the XML tag name, and the value corresponds to the text content of the XML; for the map data structure, the tag uses the attribute name as the key name.

The semantics of the current error code.

enum class Result { SUCCESS, // parse successfully ERR_EMPTY_CONTENT, // The parsing file is empty ERR_ILL_FORMED, // Illegal parsing file ERR_MISSING_FIELD, // Missing field ERR_EXTRACTING_FIELD, // Failed to parse the value ERR_TYPE, // Type error };