Events in C++

Question

I\'m not sure how to look for this online... I think they might be called something different in C++

I want to have a simple event system, somthing like

Answer 1

Take a look at the boost signal library. Combined with the function and bind libraries, you can do exactly what you are looking for.

Answer 2

I use sigslot for exactly this purpose.

Answer 3

The observer pattern from the GOF is pretty much what you want.

In the book, it has C++ code for this...

Also, as always, Boost has stuff you can make use of as well

Answer 4

There is a native Visual C++ event system. It's mostly for COM, but it has native C++ support too.

From here:

[event_source(native)]
class CSource {
public:
   __event void MyEvent(int nValue);
};

[event_receiver(native)]
class CReceiver {
public:
   void MyHandler1(int nValue) {
      printf_s("MyHandler1 was called with value %d.\n", nValue);
   }

   void MyHandler2(int nValue) {
      printf_s("MyHandler2 was called with value %d.\n", nValue);
   }

   void hookEvent(CSource* pSource) {
      __hook(&CSource::MyEvent, pSource, &CReceiver::MyHandler1);
      __hook(&CSource::MyEvent, pSource, &CReceiver::MyHandler2);
   }

   void unhookEvent(CSource* pSource) {
      __unhook(&CSource::MyEvent, pSource, &CReceiver::MyHandler1);
      __unhook(&CSource::MyEvent, pSource, &CReceiver::MyHandler2);
   }
};

int main() {
   CSource source;
   CReceiver receiver;

   receiver.hookEvent(&source);
   __raise source.MyEvent(123);
   receiver.unhookEvent(&source);
}

Answer 5

I use libsigc++. It's native for gtkmm.

A simple example losely adapted from the tutorial:

#include <iostream>
#include <sigc++/sigc++.h>

using namespace std;

class AlienDetector {
public:
        void run ();
        sigc::signal<void> signal_detected;
};

void warn_people () {
        cout << "There are aliens in the carpark!" << endl;
}

void AlienDetector::run () {
        signal_detected.emit ();
}

int main () {
        AlienDetector mydetector;
        mydetector.signal_detected.connect (sigc::ptr_fun (warn_people));
        mydetector.run ();
}

It also provides a mechanism to connect member-functions of specific objects to signals using sigc::mem_fun instead of sigc::ptr_fun:

sigc::mem_fun (someobject, &SomeClass::some_method);

This pretty much provides anything that is possible with GLib-signals.