lua_value

easy creation of Lua values and tables at the cost of some safety and speed

struct lua_value;
struct array_value;

The goal of these types is to make it easy to describe tables and arrays in C++ code. It works by using a thread local lua_State* variable inside the class so that one can simply pass values. The thread local variable is initialized by creation of a sol::state, but can also be done manually<state-automatic-handlers> with sol::set_default_state. An example of usage is below:

lua_value.cpp
  1#define SOL_ALL_SAFETIES_ON 1
  2#include <sol/sol.hpp>
  3
  4#include <iostream>
  5#include <string>
  6
  7struct int_entry {
  8	int value;
  9
 10	int_entry() : value(0) {
 11	}
 12
 13	int_entry(int v) : value(v) {
 14	}
 15
 16	std::string to_string() const {
 17		return "int_entry(" + std::to_string(value) + ")";
 18	}
 19
 20	bool operator==(const int_entry& e) const {
 21		return value == e.value;
 22	}
 23};
 24
 25int main(int, char*[]) {
 26
 27	std::cout << "=== sol::lua_value/sol::array_value ==="
 28	          << std::endl;
 29
 30	sol::state lua;
 31	lua.open_libraries(sol::lib::base, sol::lib::io);
 32
 33	sol::lua_value lv_int(lua, 56);
 34	sol::lua_value lv_int_table(lua, { 1, 2, 3, 4, 5 });
 35	sol::lua_value lv_map(lua,
 36	     { { "bark bark", "meow hiss!" },
 37	          { 3, 4 },
 38	          { ":D", 6 } });
 39	sol::lua_value lv_mixed_table(lua,
 40	     sol::array_value {
 41	          1, int_entry(2), 3, int_entry(4), 5 });
 42	sol::lua_value lv_mixed_nested_table(lua,
 43	     sol::array_value { 1,
 44	          int_entry(2),
 45	          3,
 46	          int_entry(4),
 47	          sol::array_value { 5, 6, int_entry(7), "8" } });
 48
 49	const auto& code = R"(
 50		function real_print_recursive (e, level)
 51			local et = type(e)
 52			if et == 'table' then
 53				io.write("{ ")
 54				local iters = 0
 55				for k, v in pairs(e) do
 56					if iters ~= 0  then
 57						io.write(", ")
 58					end
 59					real_print_recursive(k, level + 1)
 60					io.write(": ")
 61					real_print_recursive(v, level + 1)
 62					iters = iters + 1
 63				end
 64				io.write(" }")
 65			elseif et == 'string' then
 66				io.write('"') 
 67				io.write(e) 
 68				io.write('"')
 69			else
 70				io.write(tostring(e))
 71			end
 72			if level == 0 then
 73				io.write("\n")
 74			end
 75		end
 76
 77		function print_recursive (e)
 78			real_print_recursive(e, 0)
 79		end
 80	)";
 81
 82	sol::optional<sol::error> maybe_error
 83	     = lua.safe_script(code, sol::script_pass_on_error);
 84	if (maybe_error) {
 85		std::cerr << maybe_error->what() << std::endl;
 86		return 1;
 87	}
 88	sol::function print_recursive = lua["print_recursive"];
 89
 90	// show it printed out
 91	std::cout << "lv_int: " << std::endl;
 92	print_recursive(lv_int);
 93	std::cout << std::endl;
 94
 95	std::cout << "lv_int_table: " << std::endl;
 96	print_recursive(lv_int_table);
 97	std::cout << std::endl;
 98
 99	std::cout << "lv_map: " << std::endl;
100	print_recursive(lv_map);
101	std::cout << std::endl;
102
103	std::cout << "lv_mixed_table: " << std::endl;
104	print_recursive(lv_mixed_table);
105	std::cout << std::endl;
106
107	std::cout << "lv_mixed_nested_table: " << std::endl;
108	print_recursive(lv_mixed_nested_table);
109	std::cout << std::endl;
110
111	std::cout << std::endl;
112
113	return 0;
114}