array copy

[vadim85]

Hello,
I need to make a copy (clone) of the 1D array.

Dim array1() as F1Object
Dim copyarray() as F1Object

In my code I assigned values to the arra1

Redim copyarray(ubound(array1))

copyarray = array1

The problem is:
The copyarray changes automatically when I’m modifying the array1 because the “copyarray” is just reference to “array1”

How can I clone array1 to copyarray ?


Thank you

[LordAshes]

Well the obvious way (but not necessarily the most efficient) would be to do a content copy. Such as:

Dim Array1() as F1Object
Dim Array2() as F1Object
Dim Element as Integer

'Some code here to size and populate Array1

'Resize Array To Match The Size Of Array 1
Redim Array2(Lbound(Array1) to Ubound(Array1))

'Copy Contents
For Element = Lbound(Array1) to UBound(Array1)
Array2(Element)=Array1(Element)
Next Element


You could even wrap this up into a function which would take two arrays ByRef and perform the copy...so you could do the clone by a simple function call.

[vadim85]

Hello LordAshes

Thank you for your reply.

I already tried to copy content element by element, but the result is the same as copyarray = array1

[LaVolpe]

LordAshes, if F1Object is a object/class of some sort, that will still create an array that references the objects in the source array. Therefore, changing 1 item in Array1 will change the same/referenced item in Array2.

In VB6, there is no simple way to clone an object. You have to create a routine that creates a new instance of the class/object, then sets the clone's properties individually from the source's properties. You can build a clone function in your F1Object...

' after resizing the clone array
Dim I As Integer
For I = LBound(Array1) To UBound(Array1)
    Array1(I).Clone CopyArray(I)
Next

' in the F1Object, you'd have a function/sub similar to...
Public Sub Clone(cloneObj As Object)
    Set cloneObj = New F1Object
    cloneObj.PropertyA = Me.PropertyA
    cloneObj.PropertyB = Me.PropertyB
    ... etc
End Sub

If F1Object is not under your control, you may have to settle for doing each property individually in a routine within your form

' within your form
Private Sub Clone(srcObject As Object, dstObject As Object)
   Set dstObject = New F1Object
   dstObject.PropertyA = srcObject.PropertyA
   dstObject.PropertyB = srcObject.PropertyB
End Sub

' sample call
Dim I As Integer
' resize array
For I = LBound(Array1) To UBound(Array1)
    Clone Array1(I), CopyArray(I)
Next

Edited: Oops, forgot the most important part & updated the code above in blue

[dilettante]

An object of a Public Persistable class can be cloned pretty simply via a PropertyBag. However this involves enough code itself in the Persistable class that it's generally not worth the overhead of creating a separate registered ActiveX DLL to make this possible.

[LordAshes]

Doh! Quite correct. Sorry...I wrote the example for Byte first and then I noticed the the initial code was using F1Object instead...so I just changed it from Byte to F1Object...but, as pointed out, that won't work.

You would have to dig deeper and copy not the elements of the Object array but the actual properties themselves. I am not sure what properties the F1Object has but an example might be...

For example,

Array2(Element).Top = Array1(Element).Top
Array2(Element).Left = Array1(Element).Left
...
Array2(Element).Left = Array1(Element).Text

This, of course, makes the copy very inefficient because you basically have a O(2N) process (i.e. loop within a loop...technically the properties are not a loop but there is a number of them which will be repeated by the initial loop so it can be considered a loop within a loop).

[Merri]

In case you can tell, what kind of content F1Object holds? I'm asking this only because in some cases small changes can make it easier to clone the data. Cloning data property by property may be overly inefficient in some cases.

[LaVolpe]

In case you can tell, what kind of content F1Object holds? I'm asking this only because in some cases small changes can make it easier to clone the data. Cloning data property by property may be overly inefficient in some cases.

Agreed. In fact if one develops a class & also wants to include a clone method, then deep thought should be given as to how the property values are stored internally (arrays, udts, bitmasking, etc)