Re: functionpointers to another class

From:

anon <anon@no.invalid>

Newsgroups:

comp.lang.c++

Date:

Tue, 07 Oct 2008 11:08:04 +0200

Message-ID:

<gcf8tf$3ga$1@news01.versatel.de>

"anon" <anon@no.invalid> schrieb im Newsbeitrag
news:gcf6hq$2b0$1@news01.versatel.de...

A.Gallus wrote:

I want to define a functor which calls methods of other classes via a
function pointer:

class play

{

public:

   void operator ()

   {

       (*this.*fp)();

   }

private:

   void (OtherClass::*fp) ();

How is OtherClass defined?

};

Is this possible somehow?

Your example is missing main()

Anyway, you might want to read this:
http://www.parashift.com/c++-faq-lite/pointers-to-members.html

1. Do not top post. Read:
http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.4

2. You should increase the warning level of your compiler and read
compiler errors carefully.
I copy&paste your example, but when I tried to compile your example (g++
4.1.3 without any additional options), I got this:
b2.cpp:21: error: invalid member function declaration
b2.cpp:29: error: ISO C++ forbids declaration of ?set_fp? with no type
b2.cpp:45: error: ?::main? must return ?int?
b2.cpp: In function ?int main()?:
b2.cpp:52: error: no match for call to ?(play) ()?

Here is the fixed version of your example:

class SomeClass
{
public:
    void somefunc()
    {
    }
};
class play
{
public:
    play( SomeClass * sc ){ this->scthis = sc; }
    void operator () ()
    {
        (*scthis.*fp)();
    }
    void set_fp( void(SomeClass::*newfp)() )
    {
           this->fp = newfp;
    }
private:
    SomeClass * scthis;
    void (SomeClass::*fp) ();
};

int main()
{
    SomeClass * SC = new SomeClass();
    play * p = new play(SC);
    p->set_fp( &SomeClass::somefunc );
    (*p)();
}