Help! dynamic classes (shapeshifter)

[Timothy Stark]

Hello folks,

I am working on my program and was trying to implement 'dynamic' classes
by using virtual function calls but it did not work. I want
to convert from 'class test1' to 'class test2' without affecting
stored variables much like class shapeshifter. That's why I need
that for my own socket interface. Also I want to print "Test #2 (1)"
from 'b'. Instead it prints "Test #1 (1)".

For example,

a = new test1;
b = (test2 *)a;
c = new test2;

It results: (this program prints that:)

Test #1 (1)
Test #1 (1)
Test #2 (2)

Here is my test program.

#include <stdio.h>

class socket {
public:
int idSocket;

virtual void print(void) {}
};

class test1 : public socket
{
public:
void print(void)
{
printf("Test #1 (%d)\n", idSocket);
}
};

class test2 : public socket
{
public:
void print(void)
{
printf("Test #2 (%d)\n", idSocket);
}
};

int main(void)
{
test1 *a;
test2 *b;
test2 *c;

a = new test1;
a->idSocket = 1;
b = (test2 *)a;
c = new test2;
c->idSocket = 2;

a->print();
b->print();
c->print();

return 0;
}

Thank you!
Tim

[Ron Natalie]

Re: Help! dynamic classes (shapeshifter)


"Timothy Stark" <sword7nospam@s peakeasy.org> wrote in message news:EdadnUVRqo ZOiTqiRTvUqQ@sp eakeasy.net...
[color=blue]
> a = new test1;
> b = (test2 *)a;[/color]

This is bogus. You can't convert test1 to test2 sanely. The C-style cast
in this case ends up being a reinterpret_cas t.

Just what are you trying to accomplish? The normal paradigm is to
convert test1 and test2 instances to their common base (socket).

[Timothy Stark]

Re: Help! dynamic classes (shapeshifter)


"Ron Natalie" <ron@sensor.com > wrote in message
news:3fa6d1cf$0 $218$9a6e19ea@n ews.newshosting .com...[color=blue]
> This is bogus. You can't convert test1 to test2 sanely. The C-style[/color]
cast[color=blue]
> in this case ends up being a reinterpret_cas t.[/color]

Oh, well. Thank you. I tried that and it did not work. I have to look for
different method
to use dynamic function calls.
[color=blue]
> Just what are you trying to accomplish? The normal paradigm is to
> convert test1 and test2 instances to their common base (socket).[/color]

In my program, I want to use simple dynamic function call (callback
function) to the specific process routine from handle routine (incoming data
from TCP/IP network). I would be consider 'this->*' method. For example,
there are two different classes that inherit to that same socket class.
Will 'this->*' work on different class that inherit the socket class? How
about dynamic virtual function calls, etc? I am looking for some methods
because I am new to C++ programming.

class Socket {
public:
int idSocket;
void (*process)(char *, int);

static void Handle(void);

inline void SetCallback(voi d (*newcall)(char *, int))
{ process = newcall; }
};

class test1 : public Socket
{
:
void process2(char *, int);
void process1(char *, int);
};

class test2 : public Socket
{
:
void process3(char *, int);
void process4(char *, int);
};

void Socket::Handle( void)
{
Socket *sck;

:
:
len = read(idSocket, data, sizeof(data));
(sck->*process)(data , len);
}

Thank you!
Tim