Question

I’m working on an object-oriented Excel add-in to retrieve information from our ERP system’s database. Here is an example of a function call:

itemDescription = Macola.Item("12345").Description

Macola is an instance of a class which takes care of database access. Item() is a function of the Macola class which returns an instance of an ItemMaster class. Description() is a function of the ItemMaster class. This is all working correctly.

Items can be be stored in more than one location, so my next step is to do this:

quantityOnHand = Macola.Item("12345").Location("A1").QuantityOnHand

Location() is a function of the ItemMaster class which returns an instance of the ItemLocation class (well, in theory anyway). QuantityOnHand() is a function of the ItemLocation class. But for some reason, the ItemLocation class is not even being intialized.

Public Function Location(inventoryLocation As String) As ItemLocation
    Set Location = New ItemLocation
    Location.Item = item_no
    Location.Code = inventoryLocation
End Function

In the above sample, the variable item_no is a member variable of the ItemMaster class.

Oddly enough, I can successfully instantiate the ItemLocation class outside of the ItemMaster class in a non-class module.

Dim test As New ItemLocation
test.Item = "12345"
test.Code = "A1"
quantityOnHand = test.QuantityOnHand

Is there some way to make this work the way I want? I’m trying to keep the API as simple as possible. So that it only takes one line of code to retrieve a value.

Answer 1

Every time your function refers to Location, it creates a New ItemLocation (because it recalls the function, recursive like), or so it seems. Maybe you need to isolate the ItemMaster inside the function, like this

Public Property Get Location(inventoryLocation As String) As ItemLocation

    Dim clsReturn As ItemLocation

    Set clsReturn = New ItemLocation

    clsReturn.Item = "item_no"
    clsReturn.Code = inventoryLocation

    Set Location = clsReturn

End Property

I’m not sure why you use a function instead of a property, but if you have a good reason, I’m sure you can adapt this. I also couldn’t figure out where item_no came from, so I made it a string.