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#define SOL_ALL_SAFETIES_ON 1
#include <sol/sol.hpp>
#include <iostream>
#include <memory>
#include <mutex>
struct SomeLib {
private:
SomeLib() {}
public:
static std::shared_ptr<SomeLib> getInstance();
int doSomething() const {
return 20;
}
// destructor must be public to work with
// std::shared_ptr and friends
// if you need it to be private, you must implement
// a custom deleter with access to the private members
// (e.g., a deleter struct defined in this class)
~SomeLib() {}
};
std::shared_ptr<SomeLib> SomeLib::getInstance() {
static std::weak_ptr<SomeLib> instance;
static std::mutex m;
m.lock();
auto ret = instance.lock();
if (!ret) {
ret.reset(new SomeLib());
instance = ret;
}
m.unlock();
return ret;
}
int main(int, char*[]) {
std::cout << "=== singleton ===" << std::endl;
sol::state lua;
lua.open_libraries(sol::lib::base);
lua.new_usertype<SomeLib>("SomeLib",
"new", sol::no_constructor,
"getInstance", &SomeLib::getInstance,
"doSomething", &SomeLib::doSomething
);
lua.script(R"(
-- note we use the `.` here, not `:` (there's no self to access)
local sli = SomeLib.getInstance()
-- we use the `:` here because there is something to access
local value = sli:doSomething()
-- check
print('sli:doSomething() returned:', value)
assert(value == 20)
)");
std::cout << std::endl;
return 0;
}
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