vba - 奇怪的行为 : Variant Set to Object without using Set

Question

在将我的答案写到 VBA create IE object from ProcessID 时，我遇到了这种奇怪的行为。请注意，即使 win 变量未设置为 IWebBrowser 对象，它仍然Set 为 IWebBrowser目的。

我是不是漏掉了什么？？？ Matt、Continium、ThunderFrames...请某人告诉我这个问题吗？

Sub WierdBehavior()
    Dim win As Variant
    win = CreateObject("Shell.Application").Windows
    Debug.Print IsObject(win), TypeName(win)
End Sub

Answer 1

我能够通过让一个类返回一个接口(interface)作为其默认成员来复制该行为。感谢约翰·科尔曼和蒂姆·威廉姆斯给了我这个想法。接口(interface):IClass

VERSION 1.0 CLASS
BEGIN
  MultiUse = -1  'True
END
Attribute VB_Name = "IClass"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = False
Public Property Get getFoo() As Object
End Property

类(class):2级

VERSION 1.0 CLASS
BEGIN
  MultiUse = -1  'True
END
Attribute VB_Name = "Class2"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = False
Implements IClass
Private MyCollection As New Collection
Private Property Get IClass_getFoo() As Object
    Set Class1_getFoo = MyCollection
End Property

Public Function getInterface() As IClass
Attribute getInterface.VB_UserMemId = 0
    Set getInterface = Me
End Function

测试

Sub Test()
    Dim win As Variant
    Dim MyClass2 As New Class2
    win = MyClass2
    Debug.Print IsObject(win), TypeName(win)
End Sub

结果