stringstream problem

[janra]

If have a small function that checks date formatting, the date is of the form
ddmmyyyy. Part of it is shown below.

using namespace std;

. . .

void
CivvcDateFmt::checkDate(const string &strDate)
{
    stringstream sStrDate;
    int nDay;
    int nMnth;
    if (strDate.size() != 8)
    {
        ExInvalidDateSize EX;
        throw EX;
    }
    
    sStrDate << strDate.substr(0, 2);

    // get the day characters into an int format
    sStrDate >> nDay;
    
    if (!sStrDate.eof() || nDay > 31 || nDay < 1)
    {
        ExInvalidDay EX;
        throw EX;
    }
    
    // get the month characters into an int format
    sStrDate << strDate.substr(2, 2);
    sStrDate >> nMnth;
    cout << "Month is " << strDate.c_str() << ", " << nMnth << endl;

    . . .

The cout line produces the following output:
Month is 12, 16711680
I thought the operator>> emptied the stream but obviously it doesn't. How do I clear the stream so that it can be reused? It just seems inefficient creating 2 stringstreams.

[guestgulkan]

use the str function member passing an empty string;

For example:

stringstream sStrDate;
//put some stuff into the strinstream.
//take some stuff out
//now we want to clear any remaining garbage
sStrDate.str(""); // set stringstream to empty string 

[janra]

Ah right, thanks. I had always thought the str member was read only access.

[janra]

That doesn't seem to work. It compiles OK but the operator>> after the reassignment of str() is failing to change the value of nMnth. If I set the value of nMnth to -1, it is still -1 after line 30. I can cout the str() of the stringstream however and it has changed to the newly assigned value. It's just that the operator>> isn't working. I can put another stringstream in the code but it is annoying me now, not understanding what is going on.
I am using Netbeans with gcc 4.3.1 on Solaris 10, if that matters.

[guestgulkan]

It didn't work for me either, then I though Aha - it is a stream and we have emptied it - so it has reched End Of File.
We will need to se the stream GOOD again so that it can be re-used.

here was the test code (basically yours that I tested it with )

    string strDate("12102008"); //I assume that this is what your date format looked like
    stringstream sStrDate;
    int nDay;
    int nMnth;
   
    sStrDate << strDate.substr(0, 2);

    // get the day characters into an int format
    sStrDate >> nDay;

    // get the month characters into an int format
    sStrDate.clear(); //reset the stream  because we emptied it  earlier so it has become EOF
    sStrDate << strDate.substr(2,2);
    sStrDate >> nMnth; // now it works again
    cout << "Month is " << strDate.c_str() << ", " << nMnth << endl;
    

[janra]

That makes sense now, thanks