vba - 创建作为参数传递的类的副本

Question

我正在VBA中创建一个项目来自动处理异步准多线程(拗口，抱歉)。这涉及创建和运行一个类的多个副本，该类实现某个接口(interface)，并在异步任务完成时引发一些已知事件。接口(interface)类似于 this example

我的程序调用该类来执行其代码，并监听引发的事件，这一切都工作正常。现在，我的最终任务是获取实现适当接口(interface)的任何给定类，并制作多个副本以设置并行运行。

如何复制传递给例程的类？

如何获取类引用并创建多个新版本？

或者在代码中，我的每个线程类(处理传递的异步类的类)将有一个 Worker 属性来保存其任务。

Private workerObject As IWorker
Public Property Set Worker(workObj As IWorker) 'pass unknown class with IWorker interface
    'What goes here?
    Set workerObject = workObj
    'This won't work as then every thread points to the same worker
    'I want something to create a New one, like
    Set workerObject = New ClassOf(workObj)
    'But of course that doesn't work
End Property

Answer 1

您需要检查可能的类型并采取相应的行动:

Dim workerObject As IWorker

If TypeOf workObj Is ImplementingClass1 Then
    Set workerObject = New ImplementingClass1

ElseIf TypeOf workObj Is ImplementingClass2 Then
    Set workerObject = New ImplementingClass2

End If

或者，您可以向接口(interface)添加工厂方法:

Public Function CreateNew() As IWorker: End Function

在类中实现它:

Public Function IWorker_CreateNew() As IWorker
    Set IWorker_CreateNew = New ImplementingClass1
End Function

然后:

Set workerObject = workObj.IWorker_CreateNew()