Passing any generic function as a C++ argument [duplicate] - c++

Question

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Function pointer to member function
(8 answers)
Closed 8 years ago.
I'm trying to pass any generic function as an argument in a C++ function. As an extra layer of fun, the function is going to reside in its own separate class. In this particular case, they will all take no arguments and return void. This includes members of any generic class.
My current code reads like:
class functionsFedHere {
public:
void (*callback)();
functionsFedHere(void(*)());
}
functionsFedHere::functionsFedHere (void(*callbackFunction)()) {
callback = callbackFunction;
}
void fn1() { cout<<"Fn1"<<endl; }
class myClass {
public:
int i;
void fn2() { cout<<i<<endl; }
}
class myOtherClass {
public:
string j;
void fn3() { cout<<j<<endl; }
}
int main() {
// Initialise some objects
myClass b;
b.i = 2;
myOtherClass c;
c.j = "some text";
// Works fine with non-member functions
functionsFedHere objectA(fn1);
objectA.callback();
// Doesn't work with member functions
functionsFedHere objectB(b.fn2);
functionsFedHere objectC(c.fn3);
}
I've seen solutions like a forwarding function, or boost::bind, but as far as I can tell, I don't think these solutions will fit?
It's also worth noting that eventually I'd like to pass member functions by way of an array of pointers. For example, if myPointer[] is an array of pointers to objects of class myClass, then it would be nice to be able to write something like:
functionsFedHere objectD(myPointer[0]->fn2);
EDIT: Apparently I wasn't clear enough. This answer is not an appropriate answer, because I'm looking to pass both member and non-member functions as arguments (whereas the suggested answer is setting up a member pointer to a function that is a member of the same class).
I don't think that the forward function example will work, because the forwarding function assumes a single class type, where I'd like to pass an object of generic class.
boost::bind could well be the answer; I'm just unfamiliar with it. Can anyone point me towards some newbie-friendly reading material?
EDIT 2: Sorry, forgot to mention I'm programming on a device that is pre-C++11.

Answer 1

Use std::function:
class functionsFedHere {
public:
typedef std::function<void()> Func;
Func callback;
functionsFedHere(Func callback_) : callback(callback_) {}
};
void fn1() { cout<<"Fn1"<<endl; }
class myClass {
public:
int i;
void fn2() { cout<<i<<endl; }
};
class myOtherClass {
public:
string j;
void fn3() { cout<<j<<endl; }
};
class callableClass {
public:
void operator()() { std::cout << "in callableClass" << std::endl; }
};
int main() {
// Initialise some objects
myClass b;
b.i = 2;
myOtherClass c;
c.j = "some text";
// Works fine with non-member functions
functionsFedHere objectA(fn1);
objectA.callback();
// Works with member functions now
functionsFedHere objectB(std::bind(&myClass::fn2, b));
objectB.callback();
functionsFedHere objectC(std::bind(&myOtherClass::fn3, c));
objectC.callback();
// Works with lambdas as well
functionsFedHere objectLambda([]() { std::cout << "in lambda" << std::endl; });
objectLambda.callback();
// Works also with classes with overloaded operator()
functionsFedHere(callableClass()).callback();
return 0;
}