metatable_key¶
a key for setting and getting an object’s metatable
struct metatable_key_t {};
const metatable_key_t metatable_key;
You can use this in conjunction with sol::table to set/get a metatable. Lua metatables are powerful ways to override default behavior of objects for various kinds of operators, among other things. Here is an entirely complete example, showing getting and working with a usertype’s metatable defined by sol:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | #define SOL_ALL_SAFETIES_ON 1
#include <sol/sol.hpp>
#include "assert.hpp"
int main(int, char* []) {
struct bark {
int operator()(int x) {
return x;
}
};
sol::state lua;
lua.open_libraries(sol::lib::base);
lua.new_usertype<bark>("bark",
sol::meta_function::call_function, &bark::operator()
);
bark b;
lua.set("b", &b);
sol::table b_as_table = lua["b"];
sol::table b_metatable = b_as_table[sol::metatable_key];
sol::function b_call = b_metatable["__call"];
sol::function b_as_function = lua["b"];
int result1 = b_as_function(1);
// pass 'self' directly to argument
int result2 = b_call(b, 1);
c_assert(result1 == result2);
c_assert(result1 == 1);
c_assert(result2 == 1);
}
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