فروم بچه های تولز

اگر std::function را به صورت variadic استفاده کنید می تونید همچین چیزی رو شبیه سازی کنید.

//Signal.hpp
#ifndef SIGNAL_HPP
#define SIGNAL_HPP
#include <functional>
#include <map>
// A signal object may call multiple slots with the
// same signature. You can connect functions to the signal
// which will be called when the emit() method on the
// signal object is invoked. Any argument passed to emit()
// will be passed to the given functions.
template <typename... Args>
class Signal { public: Signal() : current_id_(0) {} // copy creates new signal Signal(Signal const& other) : current_id_(0) {} // connects a member function to this Signal template <typename T> int connect_member(T *inst, void (T::*func)(Args...)) { retu connect([=](Args... args) { (inst->*func)(args...); }); } // connects a const member function to this Signal template <typename T> int connect_member(T *inst, void (T::*func)(Args...) const) { retu connect([=](Args... args) { (inst->*func)(args...); }); } // connects a std::function to the signal. The retued // value can be used to disconnect the function again int connect(std::function<void(Args...)> const& slot) const { slots_.insert(std::make_pair(++current_id_, slot)); retu current_id_; } // disconnects a previously connected function void disconnect(int id) const { slots_.erase(id); } // disconnects all previously connected functions void disconnect_all() const { slots_.clear(); } // calls all connected functions void emit(Args... p) { for(auto it : slots_) { it.second(p...); } } // assignment creates new Signal Signal& operator=(Signal const& other) { disconnect_all(); } private: mutable std::map<int, std::function<void(Args...)>> slots_; mutable int current_id_;
};
#endif /* SIGNAL_HPP */

مثال ساده استفاده از کلاس بالا :

#include "Signal.hpp"
#include <iostream>
int main() { // create new signal Signal<std::string, int> signal; // attach a slot signal.connect([](std::string arg1, int arg2) { std::cout << arg1 << " " << arg2 << std::endl; }); signal.emit("The answer:", 42); retu 0;
}
//خروجی
//The answer: 42

دو مثال بهتر :

مثال 1:

#include "Signal.hpp"
#include <iostream>
class Button { public: Signal<> on_click;
};
class Message { public: void display() const { std::cout << "Hello World!" << std::endl; }
};
int main() { Button button; Message message; button.on_click.connect_member(&message, &Message::display); button.on_click.emit(); retu 0;
}

مثال 2 با پارامتر ورودی :

#include "Signal.hpp"
#include <iostream>
class Person {
public: Person(std::string const &name) : name_(name) {} Signal<std::string const &> say; void listen(std::string const &message) { std::cout << name_ << " received: " << message << std::endl; }
private: std::string name_;
};
int main() { Person alice("Alice"), bob("Bob"); alice.say.connect_member(&bob, &Person::listen); bob.say.connect_member(&alice, &Person::listen); alice.say.emit("Have a nice day!"); bob.say.emit("Thank you!"); retu 0;
}