Re: passing this object

From:
Mathias Gaunard <loufoque@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Fri, 28 Nov 2008 14:48:21 CST
Message-ID:
<17264bf6-b0a5-4640-a1cc-4be1b03cb7f5@c1g2000yqg.googlegroups.com>
On 28 nov, 06:02, "Jung, William" <aopiyy...@yahoo.com> wrote:

Please advice the incorrect area of the following code.

===================
class CVirtualScreen
{
public:
        CVirtualScreen();
        ~CVirtualScreen();
        Sock *sock;}


You probably want std::unique_ptr<Sock> instead of Sock* here, of
something similar.
Especially since you didn't define the correct copy constructor and
assignment operator...

boost::scoped_ptr should do for C++03.

===================
CVirtualScreen::CVirtualScreen()
{
        // QUESTION ///////////////////////////
        // IS IT CORRECT WAY OF PASSING
        // THIS OBJECT TO SOCKET CLASS??
        // SHOULD I USE & REFERENCE??
        // SHOULD I USE POINTER??
        sock = new Sock(this);


'this' is a pointer, for historical reasons.
It would probably be cleaner to pass a reference, in which case
dereference it. (*this)

// function must take std::string as parameter
CVirtualScreen::setMessage( std::string message )


You should probably take that string by const-reference.

class Sock : public CSocketComm
{
public:
Sock(CVirtualScreen screen);


That cannot compile if you pass a pointer; did you even try your code?
And you pass by value, which is nonsense since your virtual screen
shouldn't even be copiable!

Sock(CVirtualScreen& screen);

// QUESTION ///////////////////////////
// DO I DECLARE REFERENCE TO CVirtuaqlScreen LIKE THIS WAY??
CVirtuaqlScreen screen;


No, you don't.
Read a C++ book for the basics.

The syntax to declare a reference to CVirtualScreen is
CVirtualScreen& screen;

Sock::Sock(CVirtualScreen screen)
{
        // QUESTION ///////////////////////////
        // CAN I SET REFERENCE TO CVirtualScreen LIKE THIS??
        // SHOULD I USE POINTER??
        screenObject = screen
        StartServer();}


Given screenObject was not declared nor defined, that seems difficult.
Assuming your code has been corrected to declare both screen and
screenObject (which is actually your screen member I suppose) as
references, it still wouldn't work. You can only initialize references
in constructor-initializers.

void Sock::OnDataReceived(const LPBYTE lpBuffer, DWORD dwCount)
{
        // do some stuff and output the std::string object
        std::string message = ... etc
        // QUESTION ///////////////////////////
        // ONCE SOCKET PROCESSED THE MESSAGE AND EXTRACT THE DATA
        // SOCKET WILL PASS THE MESSAGE BACK TO CVirtualScreen TO
        // INSERT MESSAGE INTO A MESSAGE QUEUE
        // IS THE FOLLOWING COORECT SYNTAX TO PASS MESSAGE BACK TO
        // CVirtualScreen CLASS??
        screen.setMessage ( message );


If screen is a reference, yes, it behaves the same as the actual
value.

But really, it seems like you're trying to code in C++ by guessing
stuff.
Just learn the language.

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