implements interfaces in VBA

Hi,
I am using MS Excel and Im trying to write a macro(VBA) that would use classes and implement an interface. I have no idea what im doing wrong but i keeping getting an error prompting me that the Object module needs to implement a function that the interface has declared. But strangely the function is already implemented. My code is a follows:

clsInterface

VB Code:

Public Property Get LibraryItem_CheckedOut() As Boolean
End Property

clsDerived

VB Code:

Implements clsInterface
 
Public Sub Class_Initialize()
    MsgBox "in derived"
End Sub
 
Public Property Get LibraryItem_CheckedOut() As Boolean
    MsgBox "in derived"
End Property

And finally, ThisWorkbook

VB Code:

Dim cls As clsInterface
    Dim derived As clsDerived
    
    Set cls = New clsInterface
    Set derived = new clsDerived
    Set cls = derived

Ive wrecked my brains of this for hours and have not figured out why i get the error. Again, the error is: "Object module needs to implement 'LibraryItem_CheckedOut' for interface clsInterface

Thanks a million
raven

I might be wrong, but it looks like you're trying to use .Net code in VBA. I've never heard of Implements & Interfaces in VBA. .Net, Java, yes. Maybe the latest VBA supports that stuff?

Implements is VB6 & VBA and in .NET its there but in a different form, its in the Framework. ;)

Just like when you write an Add-In for Outlook or other Office app. It will use the Implements IDTExtensibility2 interface. This is the
same thing excep raven000 has written a custom class to implement.


Ps, Welcome to the Forums, Raven000. :)

This question is a couple months away from being 10 years old but it's still unanswered and shows up in Google search results so I wanted to answer it. The properties/functions/subs defined in the interface need to be prefixed by the interface name and an underscore. Also, it can be initialized in an easier way than initially posted. Changes below.

You can set up properties/functions/subs in the constructor(derived) class without prefixing them or putting them in the interface but they can't be called from outside the class (even if they are public) and are not visible in intellisense. When they are in the interface and the class (as public) they can be called from outside the class and are visible.

clsInterface

VB Code:

Public Property Get LibraryItem_CheckedOut() As Boolean
End Property

clsDerived

VB Code:

Implements clsInterface
 
Public Sub Class_Initialize()
    MsgBox "in derived"
End Sub
 
Public Property Get clsInterface_LibraryItem_CheckedOut() As Boolean
    MsgBox "in derived"
End Property

ThisWorkbook

VB Code:

Dim cls As clsInterface
    Set cls = New clsDerived

Sorry for bringing up such an old post but I've stumbled onto it multiple times in the last couple of years.