Collection.Add: Wrong number of arguments or invalid property assignment - vba

Question

I have a sub that creates a Collection and adds Collections inside it. But I get an Wrong number of arguments or invalid property assignment error when adding a first collection in the loop:
Sub testState()
Dim stateCopy As State
Set stateCopy = New State
stateCopy.setStateName="some name"
stateCopy.storeBudgetWorkbooks
stateCopy.storeBudgetDatas 'error on this line
End Sub
Sub storeBudgetDatas() 'inside a class named State
...
Dim year As Integer
Dim i As Integer
i = 1
For year = 2014 To 2017
Set budgetWorkbook =
ExcelApp.Application.Workbooks.Open(budgetWorkbooks(i))
MsgBox ("still here") 'this message appears
allBudgetItems.Add getBudgetData(budgetWorkbook, year) 'this line is likely to cause problems
MsgBox ("and here") 'this message doesn't appear
budgetWorkbook.Close
i = i + 1
Next
End Sub
Function getBudgetData(budgetWorkbook As Workbook, year As Integer)
...
Dim budgetItems As Collection
Set budgetItems = getBudgetItems(year)
... 'setting attributes
getBudgetData = budgetItems(year)
End Function
Function getBudgetItems(year As Integer)
...
Dim resultCollection As Collection
Set resultCollection = New Collection
Dim itemCopy As Item
Dim i As Integer
For i = LBound(budgetItemNames) To UBound(budgetItemNames)
Set itemCopy = New Item
... 'setting attributes
resultCollection.Add itemCopy
Next
Set getBudgetItems = resultCollection
End Function
I'm not sure what's wrong here. getBudgetItems returns a collection. getBudgetData returns a collection as well. I tried adding/removing parenthesis but to no avail.

Answer 1

Figured it out. There should have been Set getBudgetData = budgetItems(year) instead of getBudgetData = budgetItems(year).

Answer 2

Since you haven't shown us all the relevant parts of your code, the best I can do is guess you're missing a Set:
Function getBudgetData(budgetWorkbook As Workbook, year As Integer)
...
Dim budgetItems As Collection
Set budgetItems = getBudgetItems(year)
... 'setting attributes
Set getBudgetData = budgetItems(year) ' Need Set here
End Function