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Add a member variable

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You may add a member variable to a class using Class View. Member variables can be either for data exchange and data validation, or they can be generic. The data member variable wizard is designed to take the relevant information and use it to insert elements in your source files at the appropriate locations. You may add a member variable from the Dialog editor in Resource View, or from Class View.

Note

When you're designing and implementing a dialog box, you might find it more efficient to use the Dialog editor to add the dialog box controls, and then to implement the controls' member variables.

To add a member variable for a dialog control in Resource View using the Add Member Variable Wizard:

  1. In Resource View, expand the project node and the Dialog node to display the list of the project's dialog boxes.

  2. Double-click the dialog box to which you want to add the member variable to open it in the Dialog editor.

  3. In the dialog box displayed in the Dialog editor, right-click the control to which you want to add the member variable.

  4. On the shortcut menu, choose Add Variable to display the Add member variable wizard.

    Note

    A default value is already provided in Control ID.

  5. Provide the information in the appropriate wizard boxes. For more information, see dialog box controls and variable types.

  6. Select Finish to add the definition and implementation code to the project and close the wizard.

To add a member variable from Class View using the Add Member Variable Wizard:

  1. In Class View, expand the project node to display the classes in the project.

  2. Right-click the class to which you want to add a variable.

  3. On the shortcut menu, choose Add, and then choose Add Variable to display the Add Member Variable Wizard.

  4. Provide the information in the appropriate wizard boxes. For more information, see Add member variable wizard.

  5. Select Finish to add the definition and implementation code to the project and close the wizard.

In this section

Add member variable wizard

This wizard adds a member variable declaration to the header file. Depending on the options, it can add code to the .cpp file. Once you've added the member variable using the wizard, you can edit the code in the development environment.

  • Access

    Sets the access to the member variable. Access modifiers are keywords that specify the access other classes have to the member variable. For more information about specifying access, see member-access control. The member variable access level is set to public by default.

  • Variable type

    Sets the return type for the member variable you're adding.

    • If you're adding a member variable that isn't a dialog box control, select from the list of available types.

      For information about the types, see fundamental types.

      • char
      • double
      • float
      • int
      • long
      • short
      • unsigned char
      • unsigned int
      • unsigned long

    • If you're adding a member variable for a dialog box control, this box is filled with the type of object that is returned for a control or value. If you select Control, then Variable type specifies the base class of the control you select in the Control ID box. If the dialog box control can hold a value, and if you select Value, then Variable type specifies the appropriate type for the value that control can hold. For more information, see dialog box controls and variable types.

      This value depends on the selection in Control ID and can't be changed.

  • Variable name

    Sets the name of the member variable you're adding. Member variables typically begin with the identifying string m_, which is provided for you by default.

  • Control variable

    Indicates that the member variable manages a control within a dialog box with data exchange and data validation support. For more information, see DoDataExchange. This option is available only for member variables added to classes derived from CDialog. Select this box to activate the Control ID and Control type options.

  • Control ID

    Sets the ID for the control variable you're adding. Select from the list the ID for the type of control for which you're adding the member variable. The list is active only when the Control variable box is selected, and it's limited to IDs for the controls already added to the dialog box. For example, for the standard OK button, the Control ID is IDOK.

    Option Description
    Control This option is set by default for the control type. It manages the control itself, not the state or contents of the control (as you might want to manage for a list box, combo box, or edit box).
    Value This option is available for control types that can hold a value or show a state, such as an edit box or a check box. It's also available for control types for which you might manage range, contents, or state. For more information, see dialog box controls and variable types.

  • Category

    Specifies whether the variable is based on a control type or the value of the control.

  • Control type

    Sets the type of control being added. This box isn't available to change. For example, a button has the control type BUTTON, and a combo box has the control type COMBOBOX. For more information, see dialog box controls and variable types.

  • Max characters

    Available only when Variable type is set to CString. Indicates the most number of characters that the control can hold.

  • Min value

    Available only when the variable type is BOOL, int, UINT, long, DWORD, float, double, BYTE, short, COLECurrency or CTime. Indicates the lowest value acceptable for a scale or date range.

  • Max value

    Available only when the variable type is BOOL, int, UINT, long, DWORD, float, double, BYTE, short, COLECurrency, or CTime. Indicates the highest value acceptable for a scale or date range.

  • .h file

    For ActiveX controls, whose member variables require a wrapper class. Sets the name of the header file to add the class declaration.

  • .cpp file

    For ActiveX controls, whose member variables require a wrapper class. Sets the name of the implementation file to add the class definition.

  • Comment

    Provides a comment in the header file for the member variable.

Dialog box controls and variable types

You can use the add member variable wizard to add a member variable to a dialog box control created using MFC. The type of control for which you add the member variable determines the options that appear in the dialog box.

The following table describes all the dialog box control types that are supported in MFC and the Dialog editor. It also displays their available types and values.

Control Control type Control variable type Value variable type Min/max values (value type only)
Animation control SysAnimate32 CAnimateCtrl None; control only N/A
Button BUTTON CButton None; control only N/A
Check box CHECK CButton BOOL Min value/Max value
Combo box COMBOBOX CComboBox CString Max characters
Date time picker control SysDateTimePick32 CDateTimeCtrl CTime Min value/max value
Edit box EDIT CEdit CString, int, UINT, long, DWORD, float, double, BYTE, short, BOOL, COleDateTime, or COleCurrency Min value/max value; some support max characters
Hotkey control msctls_hotkey32 CHotKeyCtrl None; control only N/A
List box LISTBOX CListBox CString Max characters
List control SysListView32 CListCtrl None; control only N/A
Month Calendar control SysMonthCal32 CMonthCalCtrl CTime Min value/max value
Progress control msctls_progress32 CProgressCtrl None; control only N/A
Rich Edit 2 control RichEdit20A CRichEditCtrl CString Max characters
Rich Edit control RICHEDIT CRichEditCtrl CString Max characters
Scroll bar (vertical or horizontal SCROLLBAR CScrollBar int Min value/max value
Slider control msctls_trackbar32 CSliderCtrl int Min value/max value
Spin control msctls_updown32 CSpinButtonCtrl None; control only N/A
Tab control SysTabControl32 CTabCtrl None; control only N/A
Tree control SysTreeView32 CTreeCtrl None; control only N/A