I realized the significance of initializing variables in the constructor.

Meaning: The variable value can be obtained immediately when a new object is created. You do not need to try again, for example:

Void cmainframe: onmenucartrack ()
{
Cvss_logindlg DLG;
If (! (Getmodulefactoryptr ()-> connectdb (& DLG. m_dbinfo )))
Return;
CDC * Dc = This-> getdc ();
Ctrackview * ptrackview = new ctrackview ();
// Ptrackview-> ondraw (DC, DLG. m_dbinfo );
// Delete ptrackview;
 
}

This is a menu function I wrote in the car management system ~, Cvss_logindlg is the class of the dialog box used during login. After I create an object, I can directly use DLG. m_dbinfo. Instead of finding a way to get its variables (and assigning values to them, etc ~~)