Just to show an example (not using Signals2), where we can self-destruct a Functor: This is unsafe (disaster) code. /////////////////////////////////////////////////////////////////// #include <iostream> #include <map> #include <functional> #include <algorithm> using namespace std; using FuncSig = void(); using Func = function<FuncSig>; class Functor { public: Functor(map<const string, Func> *m_, const string &key_) : m{m_}, key{key_} { cout << "Functor() " << key << endl; } Functor(const Functor &other) : m{other.m}, key{other.key} { cout << "Functor(const Functor &other) " << key << endl; } ~Functor() { cout << "~Functor() " << key << endl; } void operator()() const { cout << " this == " << this << endl; cout << " key == " << key << endl; auto it = m->find(key); if (it != m->cend()) { m->erase(it); // self-destruct !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! } cout << " still running code from class (if constructor has already run, we're in deep trouble... accessing destructed data...)" << endl;; cout << " this == " << this << endl; cout << " key == " << key << endl; } private: map<const string, Func> *m; const string key; }; int main() { map<const string, Func> m; auto x = m.emplace("hello", Functor(&m, "hello")); x.first->second(); return 0; } ///////////////////////////////////////////////////////////////////