Classes and Err Object

All,

I'm struggling with handling errors within my own class modules. I was
considering the Err object, but I'm not able to error trap it.

As an example, let's say I have a Layers class and a Layer class. Within
the Layer class is code for assigning a color. You can't assign a string to
it because it's expecting a number from 1-255. So, I use
Err.Raise 1, "Not a number between 1-255."
when it receives a string.

In the Layers class, I have an AddLayer function which creates a layer given
a name and a color. So something like:
Layers.AddLayer "MyLayer", 7
will work, but
Layers.AddLayer "MyLayer", "A Color"
will raise the error.

This is working the way I expect. However, I can't use this:

On Error Resume Next
Layers.AddLayer "MyLayer", "A Color"
If Err.Number = 1 Then
Err.Clear
MsgBox "You moron, you need a number"
End If

The error still raises, and the "On Error Resume Next" statement is ignored.
Obviously, I could add test statements in the Layers class to make sure it's
passing a number, but I want the Layer class to be self-sufficient by
accepting all parameters, then raising errors for bad ones.

Am I doing something wrong, or is there a better way to handle errors within
my classes?

Thanks in advance for your help,
-Danny Polkinhorn
WATG
Honolulu

 

In VBA IDE, click "Tools->Options...", then "General" tab, in "Error
Trapping" frame, make sure "Break on Unhandked Error" is selected (it should
be default selection.

It is often helpful to set it to "Break on All Errors" while you are
developing/testing/degugging. But do remember set is back to "Break on
Unhandled Errors" before put your VBA project to production.

 

Norman,

Thanks for the reply. My error trapping settings are already that way. It
seems however that I can't trap errors that I raise within a different class
using the Err object. VBA errors are trappable, but Err object errors are
not (at least that's what I'm experiencing).

-Danny

 

Let me make it straight:

On your first post, you said the error IS raised, but not trappable, i.e.

On Error Resume Next
Layers.AddLayer "MyLayer", "A Color" '''DOES your program stops here?
If Err.Number = 1 Then
Err.Clear
MsgBox "You moron, you need a number"
End If

Try this:

On Error Resume Next
Layers.AddLayer "MyLayer", "A Color"
If Err.Number <>0 Then
MsgBox Err.Number & vbCr & Err.Description 'Show the error's
number to see if it is the number you defined
'Err.Clear
'MsgBox "You moron, you need a number"
End If

Also, why not write a small test routine to make sure your Acad VBA works
properly:

In Acad VBAIDE, add a class: Class1

Option Explicit

Public Sub Test()
Err.Raise 33333, "Class1", "Error occurs here!"
End Sub

In a new module, add following macro

Sub ErrorTest()

Dim cls As Class1
Set cls = New Class1

On Error Resume Next

cls.Test

If Err.Number <> 0 Then
MsgBox "Error raised: " & vbCr & Err.Source & vbCr &
Err.Description, vbInformation
Else
MsgBox "No Error raised", vbInformation
End If


End Sub

The raised error is captured perfectly.

So, it must be something not right in your code. If you post the code where
error is raised, the thing may be easier to be located.

 

Norman,

Thanks for the reply and your help. I hope you're still watching this
thread. Try this:

Use your Class1
Create a new class, "Class2"
Put your ErrorTest code there

Now in a module, put this code:

Sub ModuleErrorTest()

Dim clsTwo As new Class2
clsTwo.ErrorTest
Set clsTwo = Nothing

End Sub

Now if you run the module code, the error is raised and not trapped by
Class2. Any workaround, or am I making incorrect conceptual assumptions? I
really want Class2 to handle any errors because of the depth of the 'tree'.
I don't want to put error trapping at the module level in this example.

Thanks again,
Danny Polkinhorn
WATG
Honolulu