使用RemoveAll()释放嵌套的Scripting.Dictionary

Question

我在这里找到了一个主题，它回答了我正在寻找的一半：Does Scripting.Dictionary's RemoveAll() method release all of its elements first?

在我的例子中，值是Dictionary的实例，所以我嵌套了Dictionary对象的层次结构。

我的问题是，我是否需要在每个子字典上调用RemoveAll？

' just for illustration
Dim d As Dictionary
Set d = New Dictionary

Set d("a") = New Dictionary
Set d("b") = New Dictionary

' Are the next section of code necessary?
' -------------------- section start
Dim key As Variant
For Each key In d
    d.Item(key).RemoveAll
Next
' -------------------- section end

d.RemoveAll
Set d = Nothing

Answer 1

在VB6中，所有对象(通过COM)都要进行引用计数，因此，除非存在循环，否则不需要手动处理。

Answer 2

请考虑下面的代码

Option Explicit

Private m_cCache As Collection

Private Sub Form_Load()
    ' just for illustration
    Dim d As Dictionary
    Set d = New Dictionary

    Set d("a") = New Dictionary
    Set d("b") = New Dictionary

    d("b").Add "c", 123
    SomeMethod d

    ' Are the next section of code necessary?
    ' -------------------- section start
    Dim key As Variant
    For Each key In d
        d.Item(key).RemoveAll
    Next
    ' -------------------- section end

    d.RemoveAll             '--- d("b") survives
    Set d = Nothing         '--- d survives

    Debug.Print "main="; m_cCache("main").Count, "child="; m_cCache("child").Count
End Sub

Private Sub SomeMethod(d As Dictionary)
    Set m_cCache = New Collection

    m_cCache.Add d, "main"
    m_cCache.Add d("b"), "child"
End Sub

如果没有清理，区段d("b")实际上将保持不变--既不会删除子项，也不会终止实例。

Answer 3

好了，我想我可以用我做的下一个测试来回答我自己。

Sub Main()
  Dim d As Dictionary
  Dim i, j As Integer
  Dim sDummy As String * 10000
  For i = 1 To 1000
    Set d = New Dictionary      ' root dict.
    Set d("a") = New Dictionary ' child dict.
    For j = 1 To 1000
      d("a").Add j, sDummy
    Next j
    'd("a").RemoveAll
    d.RemoveAll
    Set d = Nothing
  Next i
End Sub

我注释掉了d("a").RemoveAll (我的子字典)，没有任何内存泄漏。这意味着在根(d)上调用RemoveAll就足够了，这就是我需要知道的全部内容。