luwra/examples/usertypes.cpp

#include <lua.hpp>
#include <luwra.hpp>

#include <iostream>

struct Point {
	double x, y;

	Point(double x, double y):
		x(x), y(y)
	{
		std::cout << "Construct Point(" << x << ", " << y << ")" << std::endl;
	}

	~Point() {
		std::cout << "Destruct Point(" << x << ", " << y << ")" << std::endl;
	}

	void scale(double f) {
		x *= f;
		y *= f;
	}

	std::string __tostring() const {
		return "<Point(" + std::to_string(x) + ", " + std::to_string(y) + ")>";
	}
};

int main() {
	lua_State* state = luaL_newstate();
	luaL_openlibs(state);

	// Register our user type.
	// This function also registers a garbage-collector hook and a string representation function.
	// Both can be overwritten using the third parameter, which lets you add custom meta methods.
	luwra::registerUserType<Point>(
		state,
		// Methods which shall be availabe in the Lua user data, need to be declared here
		{
			LUWRA_MEMBER(Point, scale),
			LUWRA_MEMBER(Point, x),
			LUWRA_MEMBER(Point, y)
		},
		// Meta methods may be registered aswell
		{
			LUWRA_MEMBER(Point, __tostring)
		}
	);

	// What's left, is registering a constructor for our type.
	// We have to specify which parameters our constructor takes, because there might be more than
	// one constructor to deal with.
	luwra::setGlobal(state, "Point", LUWRA_WRAP_CONSTRUCTOR(Point, double, double));

	// Load Lua code
	luaL_loadstring(
		state,
		// Instantiate type
		"local p = Point(13, 37)\n"
		"print('p =', p)\n"

		// Invoke 'scale' method
		"p:scale(2)\n"
		"print('p =', p)\n"

		// Access 'x' and 'y' property
		"print('p.x =', p:x())\n"
		"print('p.y =', p:y())\n"

		// Modify 'x' property
		"p:x(10)\n"
		"print('p.x =', p:x())\n"
	);

	// Invoke the attached script
	if (lua_pcall(state, 0, LUA_MULTRET, 0) != 0) {
		const char* error_msg = lua_tostring(state, -1);
		std::cerr << "An error occured: " << error_msg << std::endl;

		lua_close(state);
		return 1;
	} else {
		lua_close(state);
		return 0;
	}
}