vba - 将变量设置为列表中的下一个实例不起作用

Question

上下文:我正在编写 Dijkstra 的最短路径算法，只是为了练习我在 excel-vba 教程中读到的基本模式。 .

我遇到了一个有问题的情况。经过长时间调试，我发现了问题。

这是显示问题的缩小版本(已注释):

Option Explicit

Private Sub btnSolution_Click()
    Dim N As Integer: N = 3

    'Creating one list with the first cell as head
    Dim list As New model_linked_list
    Set list.next_cell = Nothing

    'Creates list 1..N
    Dim i As Integer: i = N
    Do While i > 0
        'Creates the next cell adding to the start (after the head-cell)
        Dim cell As New model_linked_list
        cell.city = i
        Set cell.next_cell = list.next_cell

        'Update head-cell
        Set list.next_cell = cell
        i = i - 1
    Loop

    'All good till here, but when I try to loop over the list:

    Dim item As model_linked_list
    Set item = list.next_cell

    'You will to set a breakpoint in this line to avoid infinite loop
    Do While Not item Is Nothing

        MsgBox item.city 'Always shows "1"

        'This is the problematic line
        Set item = item.next_cell 'It seems like it does nothing, literally
    Loop

End Sub

我的model_linked_list只是:

Option Explicit

Public city As Integer
Public next_cell As model_linked_list

举例来说，上面的代码应该只创建一个如下所示的列表:

当我尝试转到列表中的下一个单元格时，Set 似乎不起作用。有人见过这个吗？如何解决这个问题？

提前致谢。

Answer 1

你的错误在这里:

Dim cell As New model_linked_list

改成:

Dim cell As model_linked_list
Set cell = New model_linked_list

简而言之，使用 Dim cell As New model_linked_list 时，“New” 运算符仅执行一次，因此您在所有迭代中都在操作同一对象。