问题
I am trying to automatically clone an object without having to instantiate a new one and manually copy every single variable.
I remember back in the day (when I did VB6 everyday) I came up with a method of cloning objects using the PropertyBag, which was pretty cool. But I've lost the code and don't remember how to do it anymore.
Does anyone remember or have another method?
回答1:
Is this what you were looking for? Article is copied below for posterity.
Serialize Data Using a PropertyBag
You can serialize your data quickly by placing it into a PropertyBag object, then reading the PropertyBags Contents property. This property is really a Byte array that is a serial representation of the data in your PropertyBag object. You can use this byte array for many purposes, including an efficient means of data transmission over DCOM:
Private Function PackData() As String
Dim pbTemp As PropertyBag
'Create a new PropertyBag object
Set pbTemp = New PropertyBag
With pbTemp
'Add your data to the PB giving each item a
'unique string key
Call .WriteProperty("FirstName", "John")
Call .WriteProperty("MiddleInitial", "J")
Call .WriteProperty("LastName", "Doe")
'Place the serialized data into a string
'variable.
Let PackData = .Contents
End With
Set pbTemp = Nothing
End Function
To retrieve the serialized data, simply create a new PropertyBag object and set the serialized string to its Contents property. Convert the string into a byte array before assigning it to the Contents property:
Private Sub UnPackData(sData As String)
Dim pbTemp As PropertyBag
Dim arData() As Byte
'Convert the string representation of the data to
'a Byte array
Let arData() = sData
'Create a new PropertyBag object
Set pbTemp = New PropertyBag
With pbTemp
'Load the PropertyBag with data
Let .Contents = arData()
'Retrieve your data using the unique key
Let m_sFirstName = .ReadProperty("FirstName")
Let m_sMiddleInitial = _
.ReadProperty("MiddleInitial")
Let m_sLastName = .ReadProperty("LastName")
End With
Set pbTemp = Nothing
End Sub
Mike Kurtz, McKees Rocks, Pa.
回答2:
Method I have used in the past is putting all instance variables on a UDT. As long as you keep the UDT up to date you can copy a class' data with a single method/statement.
Given a "Person" class here's a simple example:
Private Type tPerson
ID As Long
FirstName As String
LastName As String
End Type
Private m_Person As tPerson
Public Sub InitPerson(ID As Long, FirstName As String, LastName As String)
m_Person.ID = ID
m_Person.FirstName = FirstName
m_Person.LastName = LastName
End Sub
Friend Sub SetData(PersonData As tPerson)
m_Person = PersonData
End Sub
Public Function GetClone() As Person
Dim p As New Person
p.SetData m_Person
Set GetClone = p
End Function
Public Property Get FirstName() As String
FirstName = m_Person.FirstName
End Property
To try the code:
Dim p As New Person
p.InitPerson 1, "MyName", "MyLastName"
Dim p2 As Person
Set p2 = p.GetClone
MsgBox p2.FirstName
If you maintain all instance varianbles inside the UDT instead of declaring them seperately you can have simple Clone method that needs very little maintenance.
Another advantage is you can put a UDT to a file handle for quick serialization to disk.
Public Sub Save(filePathName As String)
Dim f As Integer
f = FreeFile()
Open filePathName For Binary Access Write Lock Read Write As #f
Put #f, , m_Person
Close #f
End Sub
A poor men's serialization solution really :-)
回答3:
Also read: Persisting a Component's Data.
回答4:
Every object in my application's framework has a Read and Store method. What I do is pass them a stream that writes to a bytearray and store the byte array. While this doesn't eliminate having to handle every property you only have to deal with this once for reading and once for writing.
An alternative is to use a property bag like Darrel Miller says but you still have to deal with each property separately. If you already have read and store then my suggestion should save some time.
来源：https://stackoverflow.com/questions/580623/how-to-clone-an-object-in-vb6