92 lines
2.1 KiB
C++
92 lines
2.1 KiB
C++
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#define SOL_ALL_SAFETIES_ON 1
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#include <sol/sol.hpp>
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#include <map>
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#include <iostream>
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struct my_thing {
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std::map<std::string, int> m {
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{ "bark", 20 },
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{ "woof", 60 },
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{ "borf", 30 },
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{ "awoo", 5 },
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};
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my_thing() {
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}
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};
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struct lua_iterator_state {
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typedef std::map<std::string, int>::iterator it_t;
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it_t it;
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it_t last;
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lua_iterator_state(my_thing& mt)
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: it(mt.m.begin()), last(mt.m.end()) {
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}
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};
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int my_next(lua_State* L) {
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// this gets called
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// to start the first iteration, and every
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// iteration there after
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// the state you passed in pairs is argument 1
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// the key value is argument 2
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// we do not care about the key value here
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lua_iterator_state& it_state
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= sol::stack::get<sol::user<lua_iterator_state>>(L, 1);
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auto& it = it_state.it;
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if (it == it_state.last) {
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return sol::stack::push(L, sol::lua_nil);
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}
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auto itderef = *it;
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// 2 values are returned (pushed onto the stack):
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// the key and the value
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// the state is left alone
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int pushed = sol::stack::push(L, itderef.first);
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pushed += sol::stack::push_reference(L, itderef.second);
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std::advance(it, 1);
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return pushed;
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}
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int my_pairs(lua_State* L) {
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my_thing& mt = sol::stack::get<my_thing>(L, 1);
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lua_iterator_state it_state(mt);
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// pairs expects 3 returns:
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// the "next" function on how to advance,
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// the "table" itself or some state,
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// and an initial key value (can be nil)
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// next function controls iteration
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int pushed = sol::stack::push(L, my_next);
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pushed += sol::stack::push<sol::user<lua_iterator_state>>(
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L, std::move(it_state));
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pushed += sol::stack::push(L, sol::lua_nil);
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return pushed;
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}
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int main(int, char*[]) {
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std::cout << "===== pairs (using raw Lua C functions) "
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"(advanced) ====="
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<< std::endl;
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sol::state lua;
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lua.open_libraries(sol::lib::base);
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lua.new_usertype<my_thing>(
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"my_thing", sol::meta_function::pairs, &my_pairs);
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#if SOL_LUA_VERSION_I_ > 501
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lua.safe_script(R"(
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local mt = my_thing.new()
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for k, v in pairs(mt) do
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print(k, v)
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end
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)");
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#endif // Does not work on Lua 5.1 and below
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std::cout << std::endl;
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return 0;
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}
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