MessageBox class
Methods in a class module
The new class module comes with two methods:
-
runs when an object is created from this class.
-
runs when the object is destroyed.
As with methods for a form, you can use the two combo boxes at the top of the
screen to open either of these. Select from the
lefthand box and then and
will be the only two choices in the righthand
box.
Both of these are private Subs because nothing outside the class has any need
to use them. In this example there's nothing that needs to be done in either of
these methods. We need to add a Public Sub so that we can call it from the rest
of the system.
Adding the Warn method
This method will display a dialog box showing our message. It will show the
warning icon and have the name of our app as its caption.
Public Sub Warn(strMessage As String)
MsgBox
strMessage, vbExclamation, "Sample Database"
End Sub
Using the Warn method
The first thing to do is to create a MessageBox object from the class.
This only has to be done once. A class like this will be used throughout
the database so declare it as Public and set it up as the application is
loading.
Public
MessageBox
As
clsMessageBox
Set
MessageBox =
New
clsMessageBox
Now that the MessageBox object exists we can just call it any time
that we want to display a warning dialog:
MessageBox.Warn
"This is a warning."
Summary
This has been a trivial example but still useful. If you extend the MessageBox
class to include methods named Info and Stop then your code will be easier to
write and easier to read. Even after twenty years, a call to
MsgBox "Record deleted", 48, "My Application Name" still
leaves me in doubt as to whether 48 is the code for Information or Warning or Stop.
The meaning of a call to MessageBox.Warn "Record deleted"
is obvious.
I find that a fourth method named Confirm is the most useful method in my version
of this class because it makes it easier for me to get an answer from the user. The
standard messagebox returns 1, 2, 6, or 7 depending on whether you're using OK/Cancel
or Yes/No buttons. My version returns True/False so the code always reads:
If MessageBox.Confirm("Are you sure?") Then
...
rather than
If
MsgBox("Are you sure?", 36, "Sample Database") = 6
Then
...
There is less scope for me to make silly typos and the dialogs all have a consistent
style. If the client wants to change from Yes/No to OK/Cancel then I just change the
one method in MessageHandler.
To go back to an earlier way of working, this
function
shows how I did the same thing some years ago with a VBA function.
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