function as a parameter for function

[PetrP]

Hi all,

I am using Visual C++ for a long time, but I have never use it. Can somebody explain me, how to create function, which calls function, which was given as a parameter?

Something like this:

void MainFuncion(SecondFunction)
{
     LocalFunction1();
     LocalFunction2();
     ...
     SecondFunction();
}

Can somebody tell me how to do it?

Thx,

PetrP.

PS: I think that sample code will be the best way, how to learn it.

[Quintesence]

Ok here ya go

#include <stdio.h>

// is the function passed around
void Function(int Parameter)
{
printf("%u",Parameter);
}

// Receives the function pointer and calls it
void CallThisFunction(void (*FunctionPtr)(int Parameter1))
{
FunctionPtr(0);
}

void main()
{
// Call the function passing the function pointer
CallThisFunction(Function);
}

[amag]

or you could do something like:

template <typename fun_type>
void MainFunction(fun_type SecondFunction)
{
SecondFunction();
}

where fun_type can be both function pointers or classes with operator () overloaded.

[Quintesence]

Possibly, never tried it before. I'm not sure if it will work as a template. If it does it could be tricky when it comes to handling the function parameters unless you use the ... for parameter passing. I'd be interested to see if it does work.

[PetrP]

Thanks to both,

all possibilities were working fine.

First one from Quintesence was working also with parameter passing, second one form amag was also working fine until I want pass the parameters.

All these was working in console application. I tried it also in MFC classes and there were some problems. I have to little bit play with it.

But I want to add it to the DLL so no MFC will be needed .

Onece more,

thanks to both.

Petr P

[amag]

To be able to pass parameters just do:

template <typename fun_type>
void MainFunction(fun_type SecondFunction)
{
SecondFunction(10, "Hello");
}

or whatever. The compiler checks that the fun_type you pass to the function matches the arguments.
In this case

void my_fun(int k, const char *text)
{
cout << k << text << endl;
}

and then

MainFunction(my_fun);

would work just fine!