我已经尝试解决这个问题，但是找不到任何解决方案。我在一个普通模块中定义了一个UDT，并希望将其用作Class Module中的Public Sub的参数。然后我收到了编译错误：
只有在公共对象模块中定义的公共用户定义类型才能用作类模块的公共过程的参数或返回类型，或用作公共用户定义类型的字段。
然后我尝试将我的UDT移动到类中，并声明为Private。我得到了这个编译错误：
私有Enum和用户定义类型不能用作公共过程，公共数据成员或公共用户定义类型的字段的参数或返回类型。
最后，我尝试在类中声明它为Public，并收到了这个编译错误：
无法在私有对象模块中定义公共用户定义类型。
那么有没有办法让public UDT作为public sub的参数在class module中使用呢？
只需将子程序定义为 Friend 范围即可。在 VB6 类中，这对我来说编译得很好。
Private Type testtype
x As String
End Type
Friend Sub testmethod(y As testtype)
End Sub
从您的错误信息中可以看出，您的类是私有的。如果您确实希望您的类是公共的 - 例如，您正在创建一个ActiveX exe或DLL，并且希望客户端能够访问该子程序 - 那么只需将类型和子程序都设置为Public即可。
那么，有没有办法让一个公共UDT作为类中公共子程序的参数呢？
简而言之，没有。只使用Classic VB代码，你最接近的方法是创建一个复制UDT的类并使用它代替UDT。这样做有明显的优势，但如果你需要将其传递给API等，则无法实现。
另一种选择是在类型库中定义UDT。如果这样做，它可以用作公共方法的参数。
好的，如果我能让我的猫离开我，这就是如何做到的。
在Form1中（有一个命令按钮）：
Option Explicit
'
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal dst As Long, ByVal src As Long, ByVal nBytes As Long)
'
Private Sub Command1_Click()
' Okay, this is what won't work in VB6:
' Dim MyUdt1 As MyUdtType ' Declare a variable with a publicly defined UDT (no problem).
' Form2.Show ' We could have created some object with a class. This was just easier for the demo.
' INSIDE OF FORM2:
' Public Sub MySub(MyUdt2 As MyUdtType) ' It won't even let you compile this.
' Msgbox MyUdt2.l
' MyUdt2.l = 5
' End Sub
' Form2.MySub MyUdt1 ' You'll never get this far.
' Unload Form2
' Msgbox MyUdt1.l
'
' The following is a way to get it done:
'
Dim MyUdt1 As MyUdtType ' Declare a variable with a publicly defined UDT (no problem).
Dim ReturnUdtPtr As Long ' Declare a variable for a return pointer.
MyUdt1.l = 3 ' Give the variable of our UDT some value.
Form2.Show ' Create our other object.
'
' Now we're ready to call our procedure in the object.
' This is all we really wanted to do all along.
' Notice that the VarPtr of the UDT is passed and not the actual UDT.
' This allows us to circumvent the no passing of UDTs to objects.
ReturnUdtPtr = Form2.MyFunction(VarPtr(MyUdt1))
'
' If we don't want anything back, we could have just used a SUB procedure.
' However, I wanted to give an example of how to go both directions.
' All of this would be exactly the same even if we had started out in a module (BAS).
CopyMemory VarPtr(MyUdt1), ReturnUdtPtr, Len(MyUdt1)
'
' We can now kill our other object (Unload Form2).
' We probably shouldn't kill it until we've copied our UDT data
' because the lifetime of our UDT will be technically ended when we do.
Unload Form2 ' Kill the other object. We're done with it.
MsgBox MyUdt1.l ' Make sure we got the UDT data back.
End Sub
Option Explicit
'
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal dst As Long, ByVal src As Long, ByVal nBytes As Long)
'
Public Function MyFunction(ArgUdtPtr As Long) As Long
' Ok, this is how we get it done.
' There are a couple of things to notice right off the bat.
' First, the POINTER to the UDT is passed (using VarPtr) rather than the actual UDT.
' This way, we can circumvent the restriction of UDT not passed into objects.
' Second, the following MyUdt2 is declared as STATIC.
' This second point is important because the lifetime of MyUdt2 technically ends
' when we return from this function if it is just DIMmed.
' If we want to pass changes back to our caller, we will want to have a slightly longer lifetime.
Static MyUdt2 As MyUdtType
' Ok, we're here, so now we move the argument's UDT's data into our local UDT.
CopyMemory VarPtr(MyUdt2), ArgUdtPtr, Len(MyUdt2)
' Let's see if we got it.
MsgBox MyUdt2.l
' Now we might want to change it, and then pass back our changes.
MyUdt2.l = 5
' Once again, we pass back the pointer, because we can't get the actual UDT back.
' This is where the MyUdt2 being declared as Static becomes important.
MyFunction = VarPtr(MyUdt2)
End Function
Option Explicit
'
' This is just the UDT that is used for the example.
Public Type MyUdtType
l As Long
End Type
'
当错误消息指出不允许引用私有对象时，该对象确实是私有的。一旦我声明它不是私有的，并且项目模块接受了该新设置，就可以干净地编译了。
'method in the class
Public Sub CreateFile(ByRef udt1 As UdtTest)
End Sub
Public Type TPVArticulo
Referencia As String
Descripcion As String
PVP As Double
Dto As Double
End Type
在类、模块或窗体中使用Friend：
Friend Function GetArticulo() As TPVArticulo
UDT必须在公共对象中声明，例如：
Public Class Sample
Public Strucutre UDT
Dim Value As Object
End Structure
End Class