MFC – Standard I/O
”;
The MFC library provides its own version of file processing. This is done through a class named CStdioFile. The CStdioFile class is derived from CFile. It can handle the reading and writing of Unicode text files as well as ordinary multi-byte text files.
Here is the list of constructors, which can initialize a CStdioFile object −
CStdioFile(); CStdioFile(CAtlTransactionManager* pTM); CStdioFile(FILE* pOpenStream); CStdioFile(LPCTSTR lpszFileName, UINT nOpenFlags); CStdioFile(LPCTSTR lpszFileName, UINT nOpenFlags, CAtlTransactionManager* pTM);
Here is the list of methods in CStdioFile −
Sr.No. | Name & Description |
---|---|
1 |
Open Overloaded. Open is designed for use with the default CStdioFile constructor (Overrides CFile::Open). |
2 |
ReadString Reads a single line of text. |
3 |
Seek Positions the current file pointer. |
4 |
WriteString Writes a single line of text. |
Let us look into a simple example again by creating a new MFC dialog based application.
Step 1 − Drag one edit control and two buttons as shown in the following snapshot.
Step 2 − Add value variable m_strEditCtrl for edit control.
Step 3 − Add click event handler for Open and Save buttons.
Step 4 − Here is the implementation of event handlers.
void CMFCStandardIODlg::OnBnClickedButtonOpen() { // TODO: Add your control notification handler code here UpdateData(TRUE); CStdioFile file; file.Open(L"D:\MFCDirectoryDEMO\test.txt", CFile::modeRead | CFile::typeText); file.ReadString(m_strEditCtrl); file.Close(); UpdateData(FALSE); } void CMFCStandardIODlg::OnBnClickedButtonSave() { // TODO: Add your control notification handler code here UpdateData(TRUE); CStdioFile file; if (m_strEditCtrl.GetLength() == 0) { AfxMessageBox(L"You must specify the text."); return; } file.Open(L"D:\MFCDirectoryDEMO\test.txt", CFile::modeCreate | CFile::modeWrite | CFile::typeText); file.WriteString(m_strEditCtrl); file.Close(); }
Step 5 − When the above code is compiled and executed, you will see the following output.
Step 6 − Write something and click Save. It will save the data in *.txt file.
Step 7 − If you look at the location of the file, you will see that it contains the test.txt file.
Step 8 − Now, close the application. Run the same application. When you click Open, the same text loads again.
Step 9 − It starts by opening the file, reading the file, followed by updating the Edit Control.
”;