Re: Quick question!

From:

"Robby" <logicom@sympatico.ca>

Newsgroups:

microsoft.public.vc.language

Date:

Sun, 28 May 2006 15:23:44 -0700

Message-ID:

<Eppeg.202$EF1.25360@news20.bellglobal.com>

Hey David!

You did it again! :-)

*IT COMPILES WITHOUT ANY ARRORS*

So, I will try this new "Forward declaration" stuff you just tought me with
all the rest of my other pointers to objects that I want to pass to this
function. I know that Abdo mentioned it in his post as:

2. Use forward-reference *before* the #include of SFC_1.h

however this is new to me and I didn't know how to apply the syntax? However
thankyou also Abdo!

One thing though, If I do use:

class components; // forward declaration

in my SFC1.h file, what happens to all the other objects that derive from
it.... are they automatically declared also, or must I do this for all the
others too?

And David, one last question............ As a few posts back you talked
about me using the stack instead of using new which would otherwise make me
look like a Java programmer :) remember? Well.... while we are on the
subject, one of my buddies has an IT company and he says that everyone is
going on JAVA and that C++/VC++ will eventually not be very popular anymore!
This discouraged me, but I know that I must take his opinion lightly since
he is no major beer in the IT world. Anyways, I and I am sure of it for many
others, put alot of time in a language like C... what is your opinion on the
future existance of C++ and VC++?

On that note, My freind! I must say.... Its been 12 hours I am in front of
this screen! And now I must stop!

I thankyou guys very much......

Have a good weekend ...or whatever is left of it!

Very kind Regards
Roberto

"David Wilkinson" <no-reply@effisols.com> wrote in message
news:%23hxg2AqgGHA.3652@TK2MSFTNGP02.phx.gbl...

Robby wrote:

Hi David and Abdo....its just one of those days !

OKAY,

Right now this is the way I have it! Lets forget about the classes that
derive from components for now.
Just the class definition is show!

Here is the code:

======================================WndProc.h
class components
{
public:
components(){} components(int Flag); virtual ~components() {} virtual
void SYS_innitz_FLAG_AllTrueInCase(); virtual void SYS_set_SFCC(bool
bCondTrue,int AmtOfComm);
virtual int SYS_get_FLAG_AllTrueInCase()const;
virtual bool SYS_Validate_FLAG_AllTrueInCase();
static int FLAG_AllTrueInCase; protected: };
===============================================

======================================WndProc.cpp
#include "WndProc.h"

LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
PARAM wParam,
LPARAM lParam)
{
static components cp(0);

...other code...

case WM_TIMER:
cp.SYS_set_SFCC(true,1);

... other code...
}
===============================================

What I am trying to do is to take the calling of methods in the Timer
handler ex:

cp.SYS_set_SFCC(true,1);

and put them in another cpp file called "SFC_1.cpp"

So here is the whole sample again:

======================================WndProc.h
class components
{
public:
components(){} components(int Flag); virtual ~components() {} virtual
void SYS_innitz_FLAG_AllTrueInCase(); virtual void SYS_set_SFCC(bool
bCondTrue,int AmtOfComm);
virtual int SYS_get_FLAG_AllTrueInCase()const;
virtual bool SYS_Validate_FLAG_AllTrueInCase();
static int FLAG_AllTrueInCase; protected: };
=======================================

========================================WndProc.cpp
#include "WndProc.h"
#include "SFC_1.h"

LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
PARAM wParam,
LPARAM lParam)
{
static components cp(0);

...other code...

case WM_TIMER:
SFC1(&cp);

... other code...
}
====================================================

==============================================SFC_1.h
bool SFC1(components &cp);
====================================================

============================================SFC_1.cpp
#include "SFC_1.h"
#include "WndProc.h"

bool SFC1(compopnents *cp)
{

//so I can do stuff like this.... cp->SYS_set_SFCC(true,1); }
======================================================

The errors might not be exactly the same as my previous post due to some
includes I have added, however here are the errors!

c:\_DTS_PROGRAMMING\C_PROGRAMMING\vc++\MY_APPS_LAB\XPPLC\SFC_1.h(16):
error C2065: 'components' : undeclared identifier
c:\_DTS_PROGRAMMING\C_PROGRAMMING\vc++\MY_APPS_LAB\XPPLC\SFC_1.h(16):
error C2065: 'cp' : undeclared identifier
c:\_DTS_PROGRAMMING\C_PROGRAMMING\vc++\MY_APPS_LAB\XPPLC\SFC_1.h(16):
fatal error C1903: unable to recover from previous error(s); stopping
compilation

Anyways, Please get back!
appreciated!

Regards Roberto

"Robby" <Robby@discussions.microsoft.com> wrote in message
news:C8F5B8A4-D4D1-4A37-9D29-3588587F3428@microsoft.com...

Hello:

Can we pass a pointer to an object from one cpp file to another by using
a function call. Assuming the object was created and declared along with
its accessor methods in the first cpp file, but you need to manipulate
the same object in the second cpp file.

heres a quick example of the function call which calls a function
in the second cpp file:

==================cpp #1
#include "cpp2.h"
class components
{
public:
void SYS_innitz_FLAG_AllTrueInCase() {}
virtual void SYS_set_SFCC(bool bCondTrue,int AmtOfComm) {}
protected:
};

static components cp;

SFC1(&cp); //Calling a function which exists in cpp #2
=======================

==================cpp2.h - header for cpp2
void SFC1(components *cp); //Function declaration
======================
==================cpp #2
void SFC1(components *cp) //Function implementation
{}
======================

When I do this I get the obvious errors of:

c:\_DTS_PROGRAMMING\C_PROGRAMMING\vc++\MY_APPS_LAB\XPPLC\SFC_1.h(19):
error C2065: 'components' : undeclared identifier

c:\_DTS_PROGRAMMING\C_PROGRAMMING\vc++\MY_APPS_LAB\XPPLC\SFC_1.h(19):
error C2065: 'cp' : undeclared identifier

It seems that all cpp files *must* have their own class definitions, and
associated implementations... right? I do beleive that I did post this
problem before at a much larger scale, however, there could be a wrinkle
of difference in this one. Basically, just double checking!

All welcome and appreciated for the feedback....

thanks!

--
Best regards
Robert

Robby:

As Abdo has pointed out, the problem is that components is not defined or
declared in SFC_1.h . While this can be fixed bt changing the order of
includes in SFC_1.cpp, much the better way is a forward declaration:

//==============================================SFC_1.h

class components; // forward declaration
bool SFC1(components &cp);

//====================================================

I don't think this is causing you a problem here, but you might also read
about include guards (or pragma once).

David Wilkinson