vc++技术内幕（第四版）笔记（第６章）(2)
说明：
1）virtual BOOL OnInitDialog( );
//CDialog::OnInitDialog This member function is called in response to the WM_INITDIALOG message. This message is sent to the dialog box during the Create, CreateIndirect, or DoModal calls, which occur immediately before the dialog box is displayed.
//Override this member function if you need to perform special processing when the dialog box is initialized.
2）BOOL UpdateData( BOOL bSaveAndValidate = TRUE );
//CWnd::UpdateData ：Call this member function to initialize data in a dialog box, or to retrieve and validate dialog data.
//bSaveAndValidate：Flag that indicates whether dialog box is being initialized (FALSE) or data is being retrieved (TRUE).
//By default UpdateData(TRUE) is called in the default CDialog::OnOK handler and UpdateData(FALSE) is called in the default CDialog::OnInitDialog.
3）virtual void DoDataExchange( CDataExchange* pDX );
//CWnd::DoDataExchange Called by the framework to exchange and validate dialog data.
//Never call this function （DoDataExchange） directly. It is called by the UpdateData member function.
//Call UpdateData to initialize a dialog box’s controls or retrieve data from a dialog box.
4）void EndDialog( int nResult );
//CDialog::EndDialog makes the dialog box invisible but does not destroy it.
//Call this member function to terminate a modal dialog box. This member function returns nResult as the return value of DoModal（IDOK表示接受对话框数据，IDCANCEL表示取消对话框数据）. You must use the EndDialog function to complete processing whenever a modal dialog box is created.
//注意：If you implement the OK button in a modeless dialog box, you must override the OnOK member function and call DestroyWindow from within it.
5）当DoModal函数返回的时候，对话框窗口不再存在。我们可以在堆栈中创建模式对话框对象，这样就可以保证当程序控制转向到C++对话框对象所在的范围之外时，它及时的删除掉。
7，代码解释：
void CEx06aDialog::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CEx06aDialog)
DDX_Text(pDX, IDC_BIO, m_strBio);//
DDX_Radio(pDX, IDC_CAT, m_nCat);
...
DDV_MinMaxInt(pDX, m_nSsn, 0, 999999999);
//}}AFX_DATA_MAP
}
说明：
1）DoDataExchange、DDX_（交换）、DDV_（确认）函数都具有双向性。如果调用UpdateData(FALSE)（参数为FALSE），则这些数据就会将与控件相关联（值关联）的数据成员的值传递给对话框中的控件；相反，如果UpDateData(TURE)（参数是TURE），则这些函数会将数据从对话框控件中传递给与之相关联（值关联）的数据成员。
2）这里DDX_Text函数被重载，具体参阅MSDN。The DDX_Text function manages the transfer of int, UINT, long, DWORD, CString, float, or double data between an edit control in a dialog box, form view, or control view and a CString data member of the dialog box, form view, or control view object.
其它DDX_函数参阅MSDN。
