excel - 使用类的文本名称创建一个新对象

Question

有没有办法通过使用类的文本名称将对象设置为类的新实例？

我将有一个类库，并且根据其他一些变量，我想在运行时获取这些类之一。

例如我有“CTest1”、“CTest2”、“CTest3”

我会有类似于下面的功能

Function GetTestClass(lngClassNo as long) as Object
  Dim strClassName as String    
  strClassName = "CTest" & CStr(lngClassNo)
  Set GetTestClass = New instance of class(strClassName)
End Function

Answer 1

您可以使用元编程来做到这一点，尽管它看起来确实像是一个黑客。下面是一个使用几个辅助函数的示例(为了简洁而省略):

Public Function CreateInstance(typeName As String) As Object
    Dim module As VBComponent
    Set module = LazilyCreateMPCache()

    If Not FunctionExists(typeName, module) Then
        Call AddInstanceCreationHelper(typeName, module)
    End If

    Dim instanceCreationHelperName As String
    instanceCreationHelperName = module.name & ".GetInstanceOf" & typeName
    Set CreateInstance = Application.Run(instanceCreationHelperName)
End Function

Sub AddInstanceCreationHelper(typeName As String, module As VBComponent)
   Dim strCode As String
   strCode = _
   "Public Function GetInstanceOf" & typeName & "() As " & typeName & vbCrLf & _
       "Set GetInstanceOf" & typeName & " = New " & typeName & vbCrLf & _
   "End Function"
   Call AddFunction(strCode, module)
End Sub