File Writing/Reading system

**legit** · 11-22-2008

Hi again.

Since i've bypassed the login system, i've not tried to create a simple reading and writing to a file system to keep track of business records.

Here are the code snippets:

Code:

std::string DatabaseMgr::sRecordData()
{
     std::system("cls");
     std::ofstream File_Input("Record.txt", std::ios::app);
     std::cout << "Welcome, please record the data as follows:" << std::endl;
     std::cout << "\nNote! Do not place spaces inbetween words when recording\nnew products, this will crash the application!" << std::endl;
     std::cout << "\nProduct Purchased:";
     std::cin >> m_cProduct;
    /* std::cout << "\nDate the Transaction was made: ";
     std::cin >> m_sDatePurchased;
     std::cout << "\nQuantity of the Purchased Item: ";
     std::cin >> m_iQuantity;*/
     std::cin.getline(m_cProduct, 50);
     File_Input << m_cProduct << "\n";
     File_Input.close();
     std::cout << "Thank you for recording!" << std::endl;
     vReturnToStart();
}

..that is the record data function, and here is the read data funcion:

Code:

void DatabaseMgr::vReadData()
{
     std::system("cls");
     std::cout << "Here are the records you requested: " << std::endl;
     std::ifstream File_Output("Record.txt");
     while(File_Output.get(m_cBuffer))
     {
          std::cout << m_cBuffer;
     }
     std::cout << "\n\nThank you for reading our records!" << std::endl;
     File_Output.close();
     std::cin.ignore();
     vReturnToStart();
}

I C&R'd the whole program with no errors, untill i get a run-time error!

I can write to the file just fine, but my program will not let me read the text! I will post a screenie to elaborate.

Can anybody tell me what i've done wrong?

**Salem** · 11-23-2008

> std::ofstream File_Input("Record.txt", std::ios::app);
> std::ifstream File_Output("Record.txt");
An output file called "Input", and an input file called "Output" - confused yet?

> std::cin >> m_cProduct;
I bet this leaves a newline on the input stream.

> std::cin.getline(m_cProduct, 50);
> File_Input << m_cProduct << "\n";
I bet this just reads the newline, and outputs a single \n to the file.

Did you
a) open the file in a text editor to see what you had?
b) Modify your code to test whether anything was happening?
Say

Code:

 std::cout << "--" << m_cBuffer << "++" << endl;

Depending on what (if anything) you saw of "--++", it would tell you instantly a lot about of what was going on.

**execute** · 11-23-2008

Check what record.txt has... if it has text and you still cannot read it...
Then use this method of reading instead:

Code:

ifstream myfile ("example.txt");
  if (myfile.is_open())
  {
    while (! myfile.eof() )
    {
      getline (myfile,line);
      cout << line << endl;
    }
    myfile.close();
  }

**laserlight** · 11-24-2008

execute, your example code is incorrect. eof() should not be used to control the loop. Use getline() itself to control the loop.

**legit** · 11-24-2008

Originally Posted by Salem

> std:

fstream File_Input("Record.txt", std::ios::app);
> std::ifstream File_Output("Record.txt");
An output file called "Input", and an input file called "Output" - confused yet?

Yeah.. it's my way of remembering which is which

Originally Posted by Salem

> std::cin >> m_cProduct;
I bet this leaves a newline on the input stream.

> std::cin.getline(m_cProduct, 50);
> File_Input << m_cProduct << "\n";
I bet this just reads the newline, and outputs a single \n to the file.

I bet your probably right.

Originally Posted by Salem

Did you
a) open the file in a text editor to see what you had?
b) Modify your code to test whether anything was happening?

Yes I did, and there's nothing, just empty lines where the text should be

Originally Posted by Salem

Say

Code:

 std::cout << "--" << m_cBuffer << "++" << endl;

Depending on what (if anything) you saw of "--++", it would tell you instantly a lot about of what was going on.

I did do that, and i'll show you what i got as a result :

**C_ntua** · 11-24-2008

Well, you can then fill the empty lines with a text editor and test your vReadData function. Then if everything is ok you can test your sRecordData. So you can isolate what function causes the problem

**legit** · 11-24-2008

Not a bad idea, i'll get right on that :P

It's definately the sRecordData function, as I can view the data when not recording it using the databse, thanks!

**Salem** · 11-24-2008

Looks to me like m_cBuffer is a single char, because all you got was a single space first, and then a newline.

**legit** · 11-24-2008

Originally Posted by Salem

Looks to me like m_cBuffer is a single char, because all you got was a single space first, and then a newline.

It is, is that the problem?

**Salem** · 11-24-2008

Well yeah, if you were expecting it to read a line it is.

**C_ntua** · 11-24-2008

But he is reading character by character with ifstream::get

If m_cProduct and/or m_iQuantity and/or m_sDatePurchased are char that is bad. But you would get something for an output.

Character by character read should be done like this: http://www.cplusplus.com/reference/i...tream/get.html
Though, according to the above, it shouldn't work for your, since it would return a reference to a File_Output, thus non-zero. So it would crash, which it doesn't
(I feel that I have something wrong here)

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