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Hi, folks!
I want a combobox that will always display the same items regardless of where I use it, so I thought about having it be its own class, inheriting from CComboBox. Rather than remember to add the items to it in the InitDialog function for each dialog box I use it in, I want the list to fill itself when it gets created. That way, I can drop a combobox onto a dialog, then change its type from CComboBox to CMyComboBox in the class header and I'm good to go.
So, at what point in the combobox's creation sequence is the best place to put my loading function? (I'm hoping the answer will be something analogous to the InitDialog override for a dialog box class.)
(To clarify things a bit, I'm loading the list from a file, so I can't create the list items in the Resource editor.)
Thanks!
Jesse
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Why not override OnCreate for this? Let the base class handle the initialization chores and, on return, you will have a created window ready to accept AddStrings.
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Hmmm... Well, that doesn't seem to work.
I used ClassView to add a Windows Message Handler for WM_CREATE to my new ComboBox class, but the function never gets called.
M$VC added the following to my header:
protected:
//{{AFX_MSG(CRosPartNumberCB)
afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
//}}AFX_MSG
and the following to the source:
BEGIN_MESSAGE_MAP(CRosPartNumberCB, CComboBox)
//{{AFX_MSG_MAP(CRosPartNumberCB)
ON_WM_CREATE()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
/////////////////////////////////////////////////////////////////////////////
// CRosPartNumberCB message handlers
int CRosPartNumberCB::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
if (CComboBox::OnCreate(lpCreateStruct) == -1)
return -1;
AddString ("This is a test");
SelectString (-1, "This is a test");
return 0;
}
yet, a breakpoint on the above handler function never trips.
What am I missing here to get the connection established?
Jesse
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If you are using the control in a dialog, the WM_CREATE message is not sent to controls created with a dialog template. You have to override the PreSubclassWindow() function and do your initialization there. Or better yet, have an initialization function that you call from both OnCreate() and PreSubclassWindow(), that way your control will work both ways.
CPUA 0x5041
Sonork 100.11743 Chicken Little
"You're obviously a superstar." - Christian Graus about me - 12 Feb '03
Within you lies the power for good - Use it!
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Learning is a continuous process. Thanks, PJ.
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PJ,
Thanks for the insight! Yes, I was using the control in a dialog template. After overriding the function you mentioned, all is working as I wished.
Jesse
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I've got this MFC7 app I made in VS.NET and I can't get it to work right on a Win98 machine. I have a feeling I'm missing some files since VS.NET isn't installed on that machine and it is on my others. I have only tested it on WinXP so far and it all worked.
I'm using GDIPlus and MFC so I'm copying these files into my app directory: gdiplus.dll, mfc70.dll, mfc70u.dll, msvcr70.dll. I made a little setup project that uses the gdi, mfc and crt merge modules to copy these files in.
The app runs, but one of the list boxes (CListBox) is non-functional and another one works fine. Also, it adds a system tray icon but that isn't showing up in win98 either.
What's the deal?!
Fed up with MS crap!
"You must be the change you wish to see in the world." - Gandhi
articles profile
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Could it be a problem with the common controls? Try installing the latest version of Internet Explorer -- it the problem disappears most likely it is a common controls thing.
Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo
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I believe I have IE6 installed on that machine. I'll check in the morning.
Jason Henderson
"You must be the change you wish to see in the world." - Gandhi
articles profile
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I need help saving large formatted text to an Oracle database. I am currently using CLOB data type in Oracle and a CRichEditCtrl control to stream the data in and out (StreamIn, StreamOut). I got an error message when the text is more than 124 lines (default Microsoft Word document setting). Please advise.
-Elizabeth
Eilzabeth
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A CLOB should be able to hold about 2 Gig (?) of data. How are you inserting it?
Have you looked at the DBMS_LOB package?
Dave.
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Oracle CLOB holds upto 4 gigabytes data. I tried retrieving the data out using StreamIn to a CRichEditCtrl control. I am able to StreamIn and StreamOut when data is upto 1 MB (I guess). I believe there are some tricks with large data in CLOB fields. I also checked Oracle DBMS_LOB package. It is not very clear how data can be retrieved to an program interface. CLOB data is stored and retrieved in the database by using locator ids. Have you successfully implemented an interface to work with large text data?
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I am trying to implement a class for matrix multiplication:
Here is my header file:
******************************************************8
#include <stdlib.h>
class matrix
{
private:
double **m;
int nRows, nCols;
public:
matrix( int n1 = 0, int n2 = 0 );
~matrix( );
matrix& operator = ( const matrix& m1 );
matrix operator * ( const matrix& m1 );
int GetRows( ) { return nRows; }
int GetCols( ) { return nCols; }
void SetElement( int nRow, int nCol, double fValue );
double GetElement( int nRow, int nCol );
};
*********************************************************8
Here is my implementation file:
*****************************************************
#include "stdafx.h"
#include "matrix.h"
//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////
matrix::matrix( int n1, int n2 ) {
if( n1 >= 0 && n2 >= 0 ) {
printf("Constructor ...\n");
nRows = n1;
nCols = n2;
if( nRows > 0 ) {
register int nRow;
m = ( double ** ) malloc( nRows * sizeof( double * ) );
for( nRow = 0; nRow < nRows; nRow++ ) {
m[nRow] = ( double * ) malloc( nCols * sizeof( double ) );
}
}
} else {
nRows = 0;
nCols = 0;
}
}
matrix::~matrix( ) {
if( nRows > 0 ) {
while( --nRows > -1 ) {
free( m[nRows] );
}
free( m );
}
}
matrix& matrix::operator = ( const matrix& m1 ) {
printf("Assignment operator ...\n");
// If the dimensions of the matrix are not the same, redefine the matrix
if( nRows != m1.nRows || nCols != m1.nCols ) {
printf("Reshaping!");
if( nRows > 0 ) {
while( --nRows > -1 ) {
free( m[nRows] );
}
free( m );
}
nRows = m1.nRows;
nCols = m1.nCols;
if( nRows > 0 ) {
register int nRow;
m = ( double ** ) malloc( nRows * sizeof( double * ) );
for( nRow = 0; nRow < nRows; nRow++ ) {
m[nRow] = ( double * ) malloc( nCols * sizeof( double ) );
}
}
}
// Copy the elements of the matrix
register int n1, n2;
for( n1 = 0; n1 < nRows; n1++ ) {
for( n2 = 0; n2 < nCols; n2++ ) {
***********************************
* THIS IS WHERE IT FAILS !!!!
***********************************
m[n1][n2] = m1.m[n1][n2];
}
}
return *this;
}
matrix matrix::operator * ( const matrix& m1 ) {
if( nCols == m1.nRows ) {
double fValue;
register int n1, n2, n3;
matrix mResult( nRows, m1.nCols );
for( n1 = 0; n1 < nRows; n1++ ) {
for ( n2 = 0; n2 < m1.nCols; n2++ ) {
fValue = 0.0;
for ( n3 = 0; n3 < nCols; n3++ ) {
fValue += m[n1][n3] * m1.m[n3][n2];
}
mResult.m[n1][n2] = fValue;
}
}
printf("Finished multiplying ...\n");
return mResult;
} else {
printf("ERROR");
// Multiplication is impossible
}
}
void matrix::SetElement( int nRow, int nCol, double fValue ) {
if( nRow >= 0 && nRow <= nRows && nCol >= 0 && nCol <= nCols) {
m[nRow][nCol] = fValue;
}
}
double matrix::GetElement( int nRow, int nCol ) {
if( nRow >= 0 && nRow <= nRows && nCol >= 0 && nCol <= nCols) {
return m[nRow][nCol];
} else {
return 0.0;
}
}
********************************************
Here is my code:
*************************
matrix m1( 3, 2 );
m1.SetElement (0, 0, 5.0);
m1.SetElement (0, 1, 4.0);
m1.SetElement (1, 0, 3.0);
m1.SetElement (1, 1, 2.0);
m1.SetElement (2, 0, 1.0);
m1.SetElement (2, 1, 0.0);
matrix m2( 2, 2 );
m2.SetElement (0, 0, 2.3);
m2.SetElement (0, 1, 3.7);
m2.SetElement (1, 0, 4.5);
m2.SetElement (1, 1, 6.9);
printf("Before multiplication ...\n");
matrix m3( 3, 2 );
m3 = m1 * m2;
printf("After multiplication ...\n");
printf("Element: %12.10f ", m3.GetElement (0, 0));
***********************
I marked the place where it fails above. I can't figure out why. Please help!!
Many thanks
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Hi Anton,
Your class lacks a suitable copy constructor. The problem lies here:
m3 = m1 * m2; The expression m1 * m2 invokes matrix::operator *, which correctly builds the resulting matrix and returns it. But what m3 is being assigned is not that matrix, but a copy of it. As you haven't provided a copy constructor, the compiler uses the default one, which simply copies the object memberwise: so, the copied result member m really points to the same memory block as the matrix calculated in matrix::operator *; by the time matrix::operator = enters into play, the internally calculated matrix has been destroyed, and the copied result points to non-valid memory.
More generally, when any function returns an object of whatever type, what the caller of the function gets is not the internal object, but rather a copy of it. The copy constructor is always implicitly called.
The morale is: copy constructors and assignment operators come in pairs, you cannot write one without writing the other. Keep this in mind and you'll save yourself a lot of trouble.
Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo
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Joaquin:
This makes perfect sense! Thank you for pointing me in the right direction.
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World-class C++ advice! Muy bien.
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 Can any body help me figure out whats wrong with this code? All i'm trying to do is make a list of structs and then having the data in the lists printed. I havn't coded in C++ in a while so i'm assuming its the syntax
#include <fstream>
#include <iostream>
#include <iomanip> // format manipulation
#include <list> // list class library
using namespace std;
struct server
{
int server_ID;
int server_speed;
int operator==(const server&);
server& operator=(const server&);
}
int main()
{
ifstream myFile ("Request.dat", ios::in); // Don't mind this two lines
int Reqid, Artime, Cputime, server_num;
cout << "How many servers ur bitch ass wants?\n"; //Asking the user how many servers the list will consist of
cin >> server_num;
server IBM; // declare and instance of my struct
for (int i=0; i >= server_num; i++) // for each server the user requests
{ // an ID and server speed will be placed in the list
IBM.server_ID = i; // accessing the data member "ID"
IBM.server_speed = rand()% 700+100; // generating a random number for the server speed
list<server> servers;
servers.push_back (server_ID); // inputting data into list
servers.push_back (server_speed);
while (!servers.empty())
{
cout << servers.front() << " "; //printing the contents of my list
servers.pop_front();
}
cout << "\n";
/*while (!myFile.eof())
{
myFile >> Reqid >> Artime >> Cputime;
list<int> list1;
list1.push_back (Reqid);
list1.push_back (Artime);
list1.push_back (Cputime);
while (!list1.empty())
{
cout << list1.front() << ' ';
list1.pop_front();
}
*/
// Output the list values, by repeatedly getting the item from
// the "front" of the list, outputting it, and removing it
// from the front of the list.
}
return 0;
}
Sal. R
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struct server
{
int server_ID;
int server_speed;
int operator==(const server&);
server& operator=(const server&);
}
Why the operators ?
for (int i=0; i >= server_num; i++)
Don't you mean <= ???
servers.push_back (server_ID); // inputting data into list
servers.push_back (server_speed);
Shouldn't you put this info into an instance of your struct and push that back ? How can you tell what in your list is an ID and what is a speed ?
Christian
No offense, but I don't really want to encourage the creation of another VB developer.
- Larry Antram 22 Oct 2002
C# will attract all comers, where VB is for IT Journalists and managers - Michael
P Butler 05-12-2002
It'd probably be fairly easy to make a bot that'd post random stupid VB questions, and nobody would probably ever notice - benjymous - 21-Jan-2003
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Hello all,
I've wrote simple C++ program for Ms-Dos mode.
I wanna know, is there any way to run this program at startup ?
When the computer boots, and after the system checked the RAM and BIOS and CMOS, like Setup supervizer password.
I don't mean windows start up 
Regards,
My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html
Hadi Rezaie
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If you are talking about Windows 95,98,Me, you can still put things in Autoexec.bat, I believe.
You can pick your friends, and you can pick your nose, but you can't pick your friend's nose.
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Hello Navin, thanks for reply.
But i wanna run exactly after RAM testing !
as i said, like Supervizer password in Setup.
My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html
Hadi Rezaie
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Hahahahahhaha. This just shows me how old-skewl I am.
Put it in the autoexec.bat file.
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Hello Scorp1us, thanks for reply.
But i wanna run exactly after RAM testing !
as i said, like Supervizer password in Setup.
My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html
Hadi Rezaie
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