Question

出于调试原因，我想销毁一个仍然作为引用的类实例。那可能吗？它不一定非常优雅或稳定，因为它永远不会以生产代码结束。

澄清：

Public Sub Main
    Dim o as MyClass
    Set o = New MyClass //o is created, one reference
    DestroyObject o     //Class_Terminate is called and the object destroyed
    //Further code, not using o
End Sub                 //Possible runtime error here (don't care)

这可能吗？一种方法是调用IUnknown::Release手动减少引用计数，但我现在应该多久调用一次？

Answer 1

这是一个非常糟糕的主意

Option Explicit

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)

Private m_oRef As Class1

Private Sub Command1_Click()
    Dim o As Class1

    Set o = New Class1
    Set m_oRef = o
    DestroyObject o
    ' releasing m_oRef after this point will bring down the IDE '
End Sub

Private Sub DestroyObject(pArg As Object)
    Dim lRefCount       As Long
    Dim lIdx            As Long
    Dim pUnk            As IUnknown

    lIdx = ObjPtr(pArg) + &H20
    Call CopyMemory(lRefCount, ByVal lIdx, 4)
    For lIdx = 1 To lRefCount - 2
        Call CopyMemory(pUnk, pArg, 4)
        Set pUnk = Nothing
    Next
    Set pArg = Nothing
End Sub

Answer 2

如您所知，对象本身会在认为其引用计数为零时调用Class_Terminate，因此您调用Release的建议应该可以解决问题 - 只需继续调用{{1}直到Release本身抛出错误。

This page from Bruce McKinney's Hardcore Visual Basic建议一种可能的方式，有时可能获得引用计数，但我不认为你需要进入，除非这个方案（Release直到你可以“不再Release”不起作用。

“这将永远不会以生产代码结束” - 当然要小心你的假设......

即使仍有引用，我可以销毁一个类实例吗？

2 个答案: