PRB: GPF in VBA2.DLL Accessing Collection in Local Class (170357)

SYMPTOMS

With the 16-bit version of Microsoft Visual Basic 4.0, if you attempt to access a collection of a class, you may receive one of the following errors.

When running in Microsoft Windows 3.11 or Microsoft Windows For Workgroups 3.11, the error will say:

"VB caused a General Protection Fault in module VBA2.DLL"

-or-

"Run-time Error 9:
Subscript Out of Range"

When running in Microsoft Windows 95, the dialog box will report:

"An error has occurred in your program"

After clicking the "Ignore" button several times, another dialog box will report:

"Run time error '5': Invalid procedure call"

When running in Microsoft Windows NT or Windows 2000:

"An error has occurred in your application"

After clicking "Ignore" twice, you will see:

"Run time error '458'
Variable uses an OLE type not supported in Visual Basic"

When running in Microsoft Windows 98, a dialog box will report:

Run-Time error '91':
Object variable or With block variable not set

CAUSE

This error will occur under the following circumstances:

The Class module is in the same project as the code that accesses the collection. -and-
The Public property of the class module is True. -and-
The collection is not explicitly instantiated before you access it. In other words, the collection is implicitly instantiated with the New keyword when the collection is dimensioned.

RESOLUTION

To work around this problem, explicitly instantiate the collection. For example, if you are receiving one of the errors described above with the following code:

   Public MyCollection As New Collection

   Private Sub Class_Initialize()
      MyCollection.Add "Hello"
   End Sub

Change the code to look like the following:

   Public MyCollection As Collection

   Private Sub Class_Initialize()
      Set MyCollection = New Collection
      MyCollection.Add "Hello"
   End Sub

MORE INFORMATION

Steps to Reproduce Behavior

Start a new project.
Click Class Module on the Insert menu to add a class module to the project.

Type the following code in the code window of the class module:

      Public MyCollection As New Collection

      Private Sub Class_Initialize()
         MyCollection.Add "Hello"
      End Sub

With the class module active, press the F4 key to display the property sheet. Set the Public property to True.
Click Module on the Insert menu to add a module to the project.

Type the following code in the code window of the module:

      Sub Main()
         Dim obj As New Project1.Class1
         MsgBox obj.MyCollection.Item(1)
         Set obj = Nothing
      End Sub

Click Options on the Tools menu. Select the Project tab, set the Startup Form to "Sub Main" and click OK.
Press the F5 key to run the project. You will receive one of the errors described at the beginning of this article.

To work around this problem, modify the code in the class module so that it resembles the following:

      Public MyCollection As Collection

      Private Sub Class_Initialize()
         Set MyCollection = New Collection
         MyCollection.Add "Hello"
      End Sub