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Unknown class Pointer-to-Method

Started by SherlockG Jan 13, 2003 at 4:26 PM 4 replies 200+ views

Original Post

Jan 13, 2003 at 4:26 PM

Hi! I''m trying to program a registering process in which any class instance can send one of it''s method to a "call manager". So, I need to point to a method of an object. I know how I can do this for a known object type, by receiving (TMyClass::*fpFunc)... but I don''t know how to do this if I don''t know this type. I''ve read I could receive the object AND the function pointer (the adress and the offset), but I can''t make this work. Below is a code that is working for global or static __cdecl functions. //********************************************** class A; class B; class C; class A { public: A() {} ~A() {} void SomeFunction( char* SomeParam ); }; class B { public: B() {} ~B() {} void SomeOtherFunction( char* SomeParam ); }; class C { public: C() {} ~C() {} void SetFunctionPointer( void (*_fpFunc) ( char* SomeParam ) ) { fpFunc = _fpFunc; } private: void (*fpFunc) ( char* SomeParam ); }; C oC; void main( void ) { A oA; B oB; //oC.SetFunctionPointer( oA.SomeFunction ); //oC.SetFunctionPointer( oB.SomeOtherFunction ); } //********************************************** So, briefly, I want to store an unknown object adress and one of it''s method in another object, so I can call it later. Thanks for any help or hints. Let''s program! Sherlock

civguy

Jan 13, 2003 at 4:45 PM

How would you call it later? You need to have an object on which to call it after all, and since it can be a function pointer to any object's function, what object to use? If you just want to bind it to some specific object, boost::bind with boost::functionmight be what you need. Well, it's probably what you need no matter what requirements you have

Example copied from the bind page:

    
class button
{
public:

    boost::function<void> onClick;
};

class player
{
public:

    void play();
    void stop();
};

button playButton, stopButton;
player thePlayer;

void connect()
{
    playButton.onClick = boost::bind(&player::play, &thePlayer);
    stopButton.onClick = boost::bind(&player::stop, &thePlayer);
}

[edited by - civguy on January 13, 2003 5:46:39 PM]

Fruny

203

Fruny

Jan 13, 2003 at 4:56 PM

quote:

I''ve read I could receive the object AND the function pointer (the adress and the offset), but I can''t make this work.

Where ?

SherlockG

Author

SherlockG

Jan 13, 2003 at 8:08 PM

The Boost Library worked perfectly!
Thank you very much for your help!
Here is what I wanted exactly:

#include <boost/bind.hpp>
#include <boost/function.hpp>

class A
{
public:
A() {}
~A() {}

void SomeFunction() { printf( "A::SomeFunction\n" ); };
};

class B
{
// [...]
};

class C
{
public:
C() {}
~C() {}

void SetFunctionPointer( boost::function _fpFunc )
{
fpFunc = _fpFunc;
}

boost::function fpFunc;
};

A oA;
C oC;

void main( void )
{
oC.SetFunctionPointer( boost::bind(&A::SomeFunction, &oA) );
[...]
oC.whenclickedon();
}

SherlockG

Author

SherlockG

Jan 14, 2003 at 4:14 AM

I know, but the point was to be able to call from ANY class. And I don''t see every and each class of the code being inherited from a totally unuseful class.. using boost::function and boost::bind answered my problem. This is not as fast as two pointers (there are three with this) but this is not casted on each frame, so I can handle the drawbacks.

Thanks anyway!

Code, compile, pray, works! Code, compile, pray...

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