How to use signaler/listener in aGrUM ?

aGrUM has its own implementation of signalers/listeners.

Let's say that class A has a method f(int i,char ch) and would like to give to everyone the right to know whenever f() is run.

#include <agrum/core/signal/signaler2.h> // Note the '2' because the signal we
want
will send 2 args (i and ch)
class A {
 public:
  gum::signaler2<int,char> onF; // Note that onF is public !

 void f(int i,char ch) {
    //do something
  GUM_EMIT2(onF,i,ch); // a signal (with 2 args i and ch) is emitted via onF.
  }
}

Note that for class A, adding signaler is very light : a new public attribute and a GUM_EMITx when needed (where x is the number of args).

Now, how to listen to such a signal ?

#include <agrum/core/signal/listener.h>

class B : gum::listener {
 public:
  void whenF(const void *src,int i, char ch) {std::cout<<"object "<<src<<"run f
on
"<<i<<" and "<<ch<<std::endl;}
};

A a;

B b1;
B b2;

GUM_CONNECT( a,onF,b1,B::whenF );
GUM_CONNECT( a,onF,b2,B::whenF );

a.f(3,'a');
// b1.whenF and b2.whenF has been executed.

class C : gum::listener {
 public:
    void dummy(void *src,int i,char ch) {};
};

{
  C c;
  GUM_CONNECT( a,onF,c,C::dummy );
  a.f(4,'x');
  //c.dummy(), b1.whenF and b2.whenF has been executed.
} // c is destroyed...

a.f(5,'y');
//b1.whenF and b2.whenF has been executed.