VBA递归方法-退出功能未退出

Question

为什么此功能不退出？我已经尝试了Exit Function和Exit For。在到达Ubound（arr）语句后，我重置为i = 0，并且调用堆栈恢复为End Select语句，此后For循环再次开始。这一定是我执行的递归行吗？

Function AddArrToObj(ByRef arr As Variant, ByRef obj As Object, Optional ByVal i As Integer = 0)
    For i = LBound(arr) To UBound(arr)
        Select Case VBA.TypeName(obj)
            Case "Collection"
                obj.Add arr(i)
            Case "Dictionary"
                obj.Add i + 1 & " " & arr(i), arr(i)
            Case "Nothing"
                Set obj = New VBA.Collection
                Call AddArrToObj(arr, obj) 'Recursion
        End Select
        'Add Watch for i = 3 break on True
        'Why does this function not exit appropriately?
        If Not IsEmpty(obj) And i = UBound(arr) Then Exit Function
    Next i
End Function


Public Sub TestSO()
Dim collA       As VBA.Collection
Dim cmdStr      As String
cmdStr = "StackOverflow is a website."
arr = VBA.Split(cmdStr, " ")

    Call AddArrToObj(arr, collA)

End Sub

Answer 1

您可以使用递归来完成此操作，但这不必要地复杂。根据经验，仅当递归算法更易于读写时，才应在迭代中使用递归。否则，由于使用递归可能导致堆栈溢出错误，因此应使用迭代。话虽如此，这是使用递归的解决方案。我对代码进行了一些修改，使其既可以使用递归工作，又可以通过返回的集合对象进行迭代。：

    Function AddArrToObj(ByRef arr As Variant, ByRef obj As Object, Optional ByVal i As Integer = 0)
    If obj Is Nothing And i <> 0 Then
        Set obj = New Collection
    End If

    For i = LBound(arr) To UBound(arr)
        Select Case VBA.TypeName(obj)
            Case "Collection"
                obj.Add arr(i)
            Case "Dictionary"
                obj.Add i + 1 & " " & arr(i), arr(i)
            Case "Nothing"
                Set obj = AddArrToObj(arr, obj, 1) 'Recursion
                Exit For
        End Select
    Next i

    Set AddArrToObj = obj
End Function

Public Sub TestSO()
Dim collA       As VBA.Collection
Dim cmdStr      As String
Dim arr() As String
Dim obj As Object
Dim elem As Variant

cmdStr = "StackOverflow is a website."
arr = VBA.Split(cmdStr, " ")

Set obj = AddArrToObj(arr, collA)

For Each elem In obj
    Debug.Print elem
Next elem

End Sub