C / C++ / MFC

5-Feb-06 6:32

Hello everyone! Big Grin | :-D

Alright... I have this file:

<br />
|............||<br />
...............<br />
...............<br />
...............<br />
...R...........<br />
...............<br />
...............<br />
...............<br />
...............<br />
...............<br />
...............<br />
|.............|<br />

I need to read, for example, character at (4,5) (letter R). How do I do that, in standard C++? Thanks! Wink | ;-)

Lord Kixdemp
www.SulfurMidis.com
www.SulfurSoft.tk
[ftp://][http://][hotline://]tsfc.ath.cx

-- modified at 12:32 Sunday 5th February, 2006

PJ Arends5-Feb-06 11:35

PJ Arends

5-Feb-06 11:35

read the lines one at a time until you get to the required line, then get the required character

#include <iostream>
#include <fstream>
#include <string>
 
using namespace std;
 
int main(int argc, char* argv[])
{
    int row = 0;
    int col = 0;
 
    do
    {
        cout << "Enter line number ";
        cin >> row;
        cout << "Enter column number ";
        cin >> col;
 
        if (row < 1 || col < 1)
            return 0;
 
        ifstream ifs(argv[1]);
 
        string str;
        int x = 1;
        for (x = 1; x <= row && !ifs.eof(); ++x)
            ifs >> str;
 
        if (ifs.eof())
            cout << "Invalid line" << endl;
        else if (col > str.length())
            cout << "Invalid column" << endl;
        else
            cout << str.c_str()[col - 1] << endl;
        ifs.close();
    } while (1);
}

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Lord Kixdemp5-Feb-06 12:51

5-Feb-06 12:51

PJ Arends wrote:
ifs >> str;

Hmm... I don't get it... Is that suppossed to get a line? Is there a C-style equivalent? I don't want to use C++ style, it makes my EXE like 200 KB bigger! Frown | :-(

Or is it suppossed to do something else? Much thanks! Wink | ;-)

Lord Kixdemp
www.SulfurMidis.com
www.SulfurSoft.tk
[ftp://][http://][hotline://]tsfc.ath.cx

PJ Arends5-Feb-06 13:23

PJ Arends

5-Feb-06 13:23

Kixdemp wrote:
I don't want to use C++ style

In your original post you asked for standard C++, so that is what I gave you.

Kixdemp wrote:
Is that suppossed to get a line?

Yes, The C equivalent is fgets().

Lord Kixdemp5-Feb-06 16:30

5-Feb-06 16:30

PJ Arends wrote:
Kixdemp wrote:
I don't want to use C++ style

In your original post you asked for standard C++, so that is what I gave you.

Whoops, sorry, I confused terms... Blush | :O

But I'll try that if what I said in my other post doesn't work... Thanks! Wink | ;-)

Lord Kixdemp
www.SulfurMidis.com
www.SulfurSoft.tk
[ftp://][http://][hotline://]tsfc.ath.cx

Lord Kixdemp8-Feb-06 10:55

Application hangs when interrupted

8-Feb-06 10:55

string curLine;<br />
f[x] >> curLine;

That gives out errors, because f[x] is a pointer, look:

ifstream * f[3];<br />
	f[0] = new ifstream(string(map + ".ml1").c_str());<br />
	f[1] = new ifstream(string(map + ".ml2").c_str());<br />
	f[2] = new ifstream(string(map + ".ml3").c_str());

I already tried this:

string curLine;<br />
			(ifstream&)f[x] >> curLine;

But that just crashes my app... Is there a correct way to do it? Thanks! Wink | ;-)

Lord Kixdemp
www.SulfurMidis.com
www.SulfurSoft.tk
[ftp://][http://][hotline://]tsfc.ath.cx

Joel McAlduff5-Feb-06 5:46

Re: Application hangs when interrupted

5-Feb-06 5:46

I have written a few applications in VC++ 2003 that access database information via ODBC. The typical application makes various SQL requests and displays the results in a Single Document CListView, using the report style.

The programs seem to execute fine as long as they have complete focus with uninterrupted processing time. If I try to minimize the window or check my Outlook email or use some other application while the database application processes some lengthy data retrievals, the database application hangs up.

Any ideas or suggestions to make the program work more efficiently?

Thanks for any comments!

Message Closed

5-Feb-06 8:44

ddmcr

5-Feb-06 8:44

Message Closed

Joel McAlduff5-Feb-06 8:56

Retrieving data from an ODBC data source

5-Feb-06 8:56

Thanks! I had a feeling I might be headed in the direction of using threads.

SWDevil5-Feb-06 4:26

5-Feb-06 4:26

Hi,

I need to write an application that:
1. opens a database (I connect through ODBC)
2. retrieves data from a table, using an SQL query
3. enters the retrieved data into a table in a different database

So far, I wrote the following code for steps 1 and 2:

CDatabase srcDb;
if (srcDb.Open(NULL))
{
m_sDbName = srcDb.GetConnect(); //m_sDbName is a variable of type CString
UpdateData(FALSE);
}

CRecordset rs(&srcDb);
CString strSQL;
strSQL = "SELECT * FROM table1";

rs.Open(CRecordset::snapshot, strSQL, CRecordset::readOnly);
rs.Close();

Everything works OK, (the database is connected), but when it gets to the row:
rs.Open(CRecordset::snapshot, strSQL, CRecordset::readOnly);
the application crashes, and I don't understand why...

Is this the right syntax for connecting to a database and retrieving data from a table? Can someone maybe attach some source code, so I could compare...

Another question - after the row: rs.Open(CRecordset::snapshot, strSQL, CRecordset::readOnly); is executed, how do I read the data that was retrieved by the SQL query? is it in the recordset object?

Note: I am using Visual C++ 2003.

Joel McAlduff5-Feb-06 4:44

5-Feb-06 4:44

Seems like you are doing something similar, but this code works for me throughout my appliations that connect to databases via ODBC. I'm also using VC++ .Net 2003.

rs.Open(AFX_DB_USE_DEFAULT_TYPE,strSQL,CRecordset::none);

SWDevil5-Feb-06 4:52

5-Feb-06 4:52

ok - but how do I see/read the data that I retrieved with the query?

And could you maybe write the rest of your sourcecode - how did you connect to the database, how do you read the data from the query?

Thanks Smile | :)

Joel McAlduff5-Feb-06 5:22

5-Feb-06 5:22

Here is a simple example. I left out A LOT of defensive coding to keep it short. Usually I am connecting to a single database within SQL server or Oracle, so I like to do this once and keep the connection open for the duration the application is active. Thus, I use a pointer to the database object and allocate memory for this with the new command (followed by a delete command later). I am usually in and out of recordsets so I tend to just create these objects within the functions that use them.

// Create and Open the Database via ODBC
CString strDSN = "DSN=The_DomainServiceName_Here; UID=User_ID_Here; PWD=Password_Here";
CDatabase* m_pDB;
m_pDB = new CDatabase;
m_pDB->OpenEx(strDSN,CDatabase::openReadOnly);

// Create and Open a Recordset connected to the database above
CString str, strMessage;
CRecordset rs(m_pDB);
str = "SELECT SOME_FIELDS FROM SOME_TABLES WHERE BLAH BLAH... ";
rs.Open(AFX_DB_USE_DEFAULT_TYPE,str,CRecordset::none);

while (!rs.IsEOF())
{
rs.GetFieldValue("FIELD_NAME1",str);
strMessage += str;
rs.GetFieldValue("FIELD_NAME2",str);
strMessage += " ";
strMessage += str;
rs.MoveNext();
}

AfxMessageBox(strMessage);

rs.Close();

m_pDB->Close();
delete m_pDB;
m_pDB = NULL;

Hope this helps.

SWDevil5-Feb-06 20:55

5-Feb-06 20:55

Ok - thanks, it helped, but just a few questions:

1. I need to do the connection to the database from one function (when a user presses a certain button) and open the recordset in another function (when the user presses another button). How do I do this? make the CDatabase object global (a member variable)? Also, I want to get the strDSN string information from the user by opening a dialog box and letting him choose a data source. Again, how do I do this? Smile | :)

2. can I read the data from the records somehow else - not to a string?

3. does my class (in which I am doing all of this db handling) have to inherit from CRecordset?

3. what did you mean by: "I left out A LOT of defensive coding" ?

David Crow7-Feb-06 2:54

David Crow

7-Feb-06 2:54

SWDevil wrote:
...the application crashes, and I don't understand why...

Have you stepped into the Open() call to find out why?

SWDevil wrote:
Another question - after the row: rs.Open(CRecordset::snapshot, strSQL, CRecordset::readOnly); is executed, how do I read the data that was retrieved by the SQL query? is it in the recordset object?

Derive a class from CRecordset. Its member variables will hold the vales. Otherwise, using CRecordset directly will require you to use GetFieldValue().

"The greatest good you can do for another is not just to share your riches but to reveal to him his own." - Benjamin Disraeli

SWDevil7-Feb-06 5:25

7-Feb-06 5:25

yeah - I tried stepping through the code..
But now I sometimes get an error saying that columns were not bound. do you know what that means?

About the recordset - what member variables hold the values? I looked at the MSDN help and could not see any variables that actually hold any data...