Category : C++ Source Code
Archive   : TI1163.ZIP
Filename : TI1163.ASC

PRODUCT : Borland C++ NUMBER : 1163
VERSION : 3.1
OS : WIN
DATE : January 27, 1993 PAGE : 1/8

TITLE : Streaming OWL Objects to disk.




Creating persistent OWL Objects.
===============================

Borland's Object Windows Library provides a stream manager
which can be use to create persistent objects. This document
provides an example of streaming a TDialog to disk. Other
examples of persistent OWL objects are included in the examples
shipping with the product ( eg. the STEP9, STEP10 and MFILAPP
projects ). The code provided below contains a comment section
for each of the fundamemtal steps involved in creating persistent
objects. The comment includes the word 'STEP xx' when xx is a
number. Therefore, you can search for the word 'STEP' to
quickly locate the necessary steps required to included
persistency in your own application.



// ---------- //
// STRMDL.CPP //
// ---------- //

#include
#include

#include "strmdg.h"



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
class TTestWindow : public TWindow
{
PTDialog dlgPtr;
public:
TTestWindow(PTWindowsObject AParent, LPSTR ATitle);
virtual void CMTest(RTMessage Msg)
= [CM_FIRST + CM_TEST];
virtual void CMRead( RTMessage )
= [ CM_FIRST + CM_READ ];
virtual void CMWrite( RTMessage )
= [ CM_FIRST + CM_WRITE ];
BOOL IsPointerChild( void * );













PRODUCT : Borland C++ NUMBER : 1163
VERSION : 3.1
OS : WIN
DATE : January 27, 1993 PAGE : 2/8

TITLE : Streaming OWL Objects to disk.




};



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
class TTestApp : public TApplication
{
public:
TTestApp( LPSTR AName, HINSTANCE hInstance,
HINSTANCE hPrevInstance, LPSTR lpCmdLine,
int nCmdShow) :
TApplication( AName, hInstance, hPrevInstance,
lpCmdLine, nCmdShow)
{};
virtual void InitMainWindow();
};



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
TTestWindow::TTestWindow( PTWindowsObject AParent, LPSTR ATitle )
: TWindow( AParent, ATitle )
{
AssignMenu( "COMMANDS" );
dlgPtr = NULL;
}



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
void TTestWindow::CMTest( RTMessage )
{
/* --------------- [ STEP 1 ] ------------------ *\
Construct an actual TDialog to stream out
\* ----------------------------------------------- */
dlgPtr = new TDialog( this , "TESTDIALOG" );
GetApplication()->MakeWindow( dlgPtr );













PRODUCT : Borland C++ NUMBER : 1163
VERSION : 3.1
OS : WIN
DATE : January 27, 1993 PAGE : 3/8

TITLE : Streaming OWL Objects to disk.




}



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
static int Test( void *child , void *test_child )
{
return( test_child == child );
}



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
BOOL TTestWindow::IsPointerChild( void * child )
{
if ( FirstThat( Test , child ) )
return TRUE;
else
return FALSE;
}



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
void TTestWindow::CMWrite( RTMessage)
{
/* ---------------------------------- *\
Test to see if the dialog pointer
currently represents a real
window
\* ---------------------------------- */
if ( IsPointerChild( dlgPtr ) )
{

/* --------------- [ STEP 2 ] ------------------ *\
















PRODUCT : Borland C++ NUMBER : 1163
VERSION : 3.1
OS : WIN
DATE : January 27, 1993 PAGE : 4/8

TITLE : Streaming OWL Objects to disk.




Open up a opstream, in this case we are using
a ofpstream to write the dialog data to a
file.
\* ----------------------------------------------- */
ofpstream ofp( "file.dia" );
if ( ofp )
{


/* ----------------- [ STEP 3 ] -------------------- *\
Here we are writing a pointer out. We are using
the << operator which takes a opstream& and a
TStreamble*. Common errors include not using the
correct << operator by either writing ones one
which explicitly takes a TDialog *, etc.
\* --------------------------------------------------- */
ofp << ( TStreamable* )dlgPtr;
ofp.close();
}
else
MessageBox( HWindow ,
"Opening ofpstream failed",
"Error", MB_OK );
}
else
MessageBox( HWindow ,
"Choose Test to bring up the dialog first",
"Error", MB_OK );
}



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
void TTestWindow::CMRead( RTMessage )
{
/* ----------------- [ STEP 4 ] -------------------- *\
Open an ipstream to read the object back from.
\* --------------------------------------------------- */
ifpstream ifp( "file.dia" );
if ( ifp )
{













PRODUCT : Borland C++ NUMBER : 1163
VERSION : 3.1
OS : WIN
DATE : January 27, 1993 PAGE : 5/8

TITLE : Streaming OWL Objects to disk.




PTDialog new_dialog = 0;

/* ----------------- [ STEP 5 ] -------------------- *\
Read the object back from the ipstream. It is
important to use the >> operator which takes a
ipstream & and void * & as parameters. If you get
warnings about temporary objects here, something
is probably wrong!. Notice how we have not called
a constructor for new_dialog. The stream manager
is going to call new TDialog( streamableInit ) for
us. It knows to do this because the ifpstream has
the class name for TDialog in it. The stream
manager can look up that class name in a database
and find the build function. The build function
constructs our object for us. TDialog gave the
stream manger this information by constructing a
TStreamableClass object. Since we are passing a
reference to our pointer, the stream manager will
be able to modify our pointer to point to the
newly allocated object. Common errors are using
the wrong operator here, or typecasting to a
TStreamable*.
\* --------------------------------------------------- */
ifp >> ( void * & ) new_dialog;

/* ----------------- [ STEP 6 ] -------------------- *\
TWindowsObject::write does not save the Parent
pointer, it will be set to NULL after reading back
from the ipstream. This will cause the dialog to
appear in the wrong place. We are explicitly
setting the parent again here.
\* --------------------------------------------------- */
new_dialog->Parent = this;
if ( new_dialog )
{
/* ----------------- [ STEP 7 ] -------------------- *\
Now that the object is constructed, you can do a
MakeWindow on it.
\* --------------------------------------------------- */
GetApplication()->MakeWindow( new_dialog );
}
else
MessageBox( HWindow ,













PRODUCT : Borland C++ NUMBER : 1163
VERSION : 3.1
OS : WIN
DATE : January 27, 1993 PAGE : 6/8

TITLE : Streaming OWL Objects to disk.




"Bad dialog pointer",
"Error" , MB_OK );
}
else
MessageBox( HWindow ,
"Bad ifpstream",
"Error", MB_OK );
}



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
void TTestApp::InitMainWindow()
{
MainWindow = new TTestWindow( NULL, Name );
}



// ----------------------------------------------------- //
// //
// ----------------------------------------------------- //
int PASCAL WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow )
{
TTestApp TestApp( "Streaming Dialog Tester",
hInstance, hPrevInstance,
lpCmdLine, nCmdShow );
TestApp.Run();
return( TestApp.Status );
}






// -------- //
// STRMDG.H //
// -------- //
#ifndef __STRMDG_H













PRODUCT : Borland C++ NUMBER : 1163
VERSION : 3.1
OS : WIN
DATE : January 27, 1993 PAGE : 7/8

TITLE : Streaming OWL Objects to disk.




#define __STRMDG_H

#define ID_LISTBOX 101
#define ID_BUTTON 102

#define CM_TEST 201
#define CM_READ 202
#define CM_WRITE 203

#endif // __STRMDG_H






// ---------- //
// STRMDG.DEF //
// ---------- //
NAME OWL_Sample_Application
DESCRIPTION 'Sample OWL Dialog Streaming'
EXETYPE WINDOWS
CODE PRELOAD MOVEABLE DISCARDABLE
DATA PRELOAD MOVEABLE MULTIPLE
HEAPSIZE 1024
STACKSIZE 5120






// --------- //
// STRMDG.RC //
// --------- //
#include
#include "strmdg.h"

COMMANDS MENU LOADONCALL MOVEABLE PURE DISCARDABLE
BEGIN
MENUITEM "&Dialog", CM_TEST
MENUITEM "&Write", CM_WRITE
MENUITEM "&Read" , CM_READ













PRODUCT : Borland C++ NUMBER : 1163
VERSION : 3.1
OS : WIN
DATE : January 27, 1993 PAGE : 8/8

TITLE : Streaming OWL Objects to disk.




END


TESTDIALOG DIALOG DISCARDABLE LOADONCALL PURE MOVEABLE 30, 49,
188, 100
STYLE WS_POPUP | WS_DLGFRAME | WS_VISIBLE
BEGIN
CONTROL "&Fill List Box" ID_BUTTON, "BUTTON", WS_CHILD |
WS_VISIBLE | WS_TABSTOP, 111, 13, 68, 12
CONTROL "&Cancel" IDCANCEL, "BUTTON", WS_CHILD | WS_VISIBLE |
WS_TABSTOP, 112, 66, 68, 12
CONTROL "COMBOBOX" ID_LISTBOX, "COMBOBOX", WS_CHILD |
WS_VISIBLE | CBS_DROPDOWN | WS_BORDER | WS_VSCROLL |
0x3L, 8, 8, 83, 73
END






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subject to the terms of the No-Nonsense License Statement that
you received with the Borland product to which this information
pertains.