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Chapter 8: Object-Oriented Programming
14_046500 ch08.qxp 12/5/06 5:36 PM Page 193

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Monitoring data change is an important event. You might need to perform
verification or to modify other object settings when a data change occurs.
For example, when you decide to change the button style, you also need
to check the default button setting to ensure that it falls within the desired
range. Listing 8-3 shows a typical example of a data modification event.
Listing 8-3
Creating an Object Event
Public Static Property Let Buttons(Value As ButtonTypes)
‘ Change the value of the message button based on the
‘ input value.
Select Case Value
Case OKOnly
UseButtons = vbOKOnly
Case OKCancel
UseButtons = vbOKCancel
Case AbortRetryIgnore
UseButtons = vbAbortRetryIgnore
Case YesNoCancel
UseButtons = vbYesNoCancel
Case YesNo
UseButtons = vbYesNo
Case RetryCancel
UseButtons = vbRetryCancel
End Select
‘ Raise an event to show the button type has changed.
RaiseEvent ChangeButton(Value)
End Property
Notice in this code and in the code in the earlier “Defining methods” section
that the 
RaiseEvent
method isn’t called until after the action takes place.
Always raise the event after you verify that it has occurred. Otherwise, you
might react to an event that hasn’t taken place yet (and might not take place
at all).
Using enumerated constants
The example uses a number of enumerated constants. These constants serve
to limit the number of acceptable input values. They also act as reminders of
the acceptable inputs. Listing 8-4 contains an example of a public enumeration.
Listing 8-4
Using Constants in an Object
‘ This enumeration shows the button types.
Public Enum ButtonTypes
OKOnly = 0
OKCancel = 1
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