[RESOLVED] Is it possible to add an enumerator to an array?

I wonder if there is a way to add an enumerator to a VB array, for example:

Code:

---

For Each vArrayItem In vArray
    'Do something
Next

---

Class1

Code:

---

Option Explicit

Private mItems() As Variant

Public Property Get Item(ByVal Index As Long) As Variant
    Item = mItems(Index)
End Property

Public Property Let Item(ByVal Index As Long, NewVal As Variant)
    mItems(Index) = NewVal
End Property

Public Function NewEnum() As IUnknown
  Set NewEnum = mItems.[_NewEnum]
End Function

Private Sub Class_Initialize()
    mItems = Array(10)
End Sub

---

Thanks.

IIRC, it is possible, but as a Property Get not a Function
I think it was something like this:
Tools|Procedure Attributes then click Advanced
Select NewEnum
Set Procedure ID to -4

Hi Zvoni, I tried your method and it still doesn't seem to work. The system prompts "Object required"

It only works for collections isn't it? Doesn't work for arrays in the class.

Quote:

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Originally Posted by Arnoutdv

It only works for collections isn't it? Doesn't work for arrays in the class.

---

IIRC, it works for your own "Collection"-Classes, too (independent if internally it's a collection or an array)
I remember doing something like that some 15 years ago, but i don't have the source-code anymore (at least i haven't seen it in 15 years).
Bruce McKinney had an example in his HVB-Book

EDIT: Found Bruce's Source-Code from HVB

Code:

---

Public Function NewEnum() As IEnumVARIANT
Attribute NewEnum.VB_UserMemId = -4

---

I know it works for looping thru an array.
I never saw a sample for the NewEnum on a variant array in a class.

Did some searching, maybe this can be used as a skeleton:
http://www.mvps.org/vbvision/Super_Collections.htm

Arnout,

yeah, kind looks familiar with the mentioned hacks

Quote:

---

Originally Posted by Arnoutdv

I know it works for looping thru an array.
I never saw a sample for the NewEnum on a variant array in a class.

Did some searching, maybe this can be used as a skeleton:
http://www.mvps.org/vbvision/Super_Collections.htm

---

Hi Arnoutdv, I downloaded and read the code from the link you provided, it's too complicated, I decided to give up adding an enumerator to the VB array. Thank you, Arnoutdv. Thank Zvoni too.

Quote:

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Originally Posted by dreammanor

I decided to give up adding an enumerator to the VB array.

---

One easy way is, to return the "Array itself" via an Items-Property (since VB can enumerate on its own SafeArrays).

Class1-Code:

Code:

---

Option Explicit
 
Private mItems() As Variant
 
Private Sub Class_Initialize()
  mItems = Array() 'inits the array (though still with no members)
End Sub

Public Sub push(Item)
  ReDim Preserve mItems(0 To UBound(mItems) + 1): mItems(UBound(mItems)) = Item
End Sub
Public Property Get length() As Long
  length = UBound(mItems) + 1
End Property

Public Property Get Item(ByVal Index As Long) As Variant '<- usually with Default-Attribute set
  Item = mItems(Index)
End Property
Public Property Let Item(ByVal Index As Long, RHS As Variant)
  mItems(Index) = RHS
End Property

Public Property Get Items() As Variant()
  Items = mItems
End Property

---

And Test-Form-Code:

Code:

---

Private Sub Form_Load()
  Dim Arr As New Class1, V
      Arr.push 1
      Arr.push 2
      Arr.push 3
 
  Debug.Print "Arr-length: "; Arr.length
 
  For Each V In Arr.Items '<- but Items needs to be specified explicitely then
    Debug.Print V
  Next
End Sub

---

Another variant for "easy enumerations" would be, to use an RC5-Helper for that,
(in conjunction with "flagging" the Enumerator-method of the Class with AttributeID= -4)
Class1-Code:

Code:

---

Option Explicit

Implements IEnumerable 'we implement the IEnumerable-Interface from RC5

Private mItems() As Variant

Private Sub Class_Initialize()
  mItems = Array() 'inits the array (though still with no members)
End Sub

Public Sub push(Item)
  ReDim Preserve mItems(0 To UBound(mItems) + 1): mItems(UBound(mItems)) = Item
End Sub
Public Property Get length() As Long
  length = UBound(mItems) + 1
End Property

Public Property Get Item(ByVal Index As Long) As Variant '<- usually with Default-Attribute set
  Item = mItems(Index)
End Property
Public Property Let Item(ByVal Index As Long, RHS As Variant)
  mItems(Index) = RHS
End Property

Public Property Get Items() As Variant()
  Items = mItems
End Property

Public Function NewEnum() As IUnknown '<- needs Enumerable-ProcAttribute: -4
  Set NewEnum = New_c.EnumerateOn(Me, UBound(mItems) + 1)
End Function
Private Function IEnumerable_NextItem(Idx As Long) As Variant 'this is the IEnumerable-Callback
  IEnumerable_NextItem = mItems(Idx)
End Function

---

And Test-Form-Code again:

Code:

---

Private Sub Form_Load()
  Dim Arr As New Class1, V
      Arr.push 1
      Arr.push 2
      Arr.push 3
 
  Debug.Print "Arr-length: "; Arr.length
 
  For Each V In Arr.Items '<- but Items needs to be specified explicitely then
    Debug.Print V
  Next
 
  For Each V In Arr '<- now one can also directly enumerate on Arr
    Debug.Print V
  Next
End Sub

---

HTH

Olaf

http://www.vbforums.com/showthread.p...hout-a-typelib

Here is a "raw" implementation of a handy IEnumVARIANT light-weight object. It just forwards IEnumVARIANT::Next to parent object's default method with some code like this

VariantCopyToPtr rgVar, .Enumerable(.Index)

. . . so this trades the need to implement a custom IEnumerable interface for a bit of speed.

Of course RC5's solution is probably a lot more stable in the IDE as first it's a compiled DLL and second it's been excercised a bit more in the wild for some years now.

cheers,
</wqw>

Quote:

---

Originally Posted by Schmidt

One easy way is, to return the "Array itself" via an Items-Property (since VB can enumerate on its own SafeArrays).

Class1-Code:

Code:

---

Option Explicit
 
Private mItems() As Variant
 
Private Sub Class_Initialize()
  mItems = Array() 'inits the array (though still with no members)
End Sub

Public Sub push(Item)
  ReDim Preserve mItems(0 To UBound(mItems) + 1): mItems(UBound(mItems)) = Item
End Sub
Public Property Get length() As Long
  length = UBound(mItems) + 1
End Property

Public Property Get Item(ByVal Index As Long) As Variant '<- usually with Default-Attribute set
  Item = mItems(Index)
End Property
Public Property Let Item(ByVal Index As Long, RHS As Variant)
  mItems(Index) = RHS
End Property

Public Property Get Items() As Variant()
  Items = mItems
End Property

---

And Test-Form-Code:

Code:

---

Private Sub Form_Load()
  Dim Arr As New Class1, V
      Arr.push 1
      Arr.push 2
      Arr.push 3
 
  Debug.Print "Arr-length: "; Arr.length
 
  For Each V In Arr.Items '<- but Items needs to be specified explicitely then
    Debug.Print V
  Next
End Sub

---

Another variant for "easy enumerations" would be, to use an RC5-Helper for that,
(in conjunction with "flagging" the Enumerator-method of the Class with AttributeID= -4)
Class1-Code:

Code:

---

Option Explicit

Implements IEnumerable 'we implement the IEnumerable-Interface from RC5

Private mItems() As Variant

Private Sub Class_Initialize()
  mItems = Array() 'inits the array (though still with no members)
End Sub

Public Sub push(Item)
  ReDim Preserve mItems(0 To UBound(mItems) + 1): mItems(UBound(mItems)) = Item
End Sub
Public Property Get length() As Long
  length = UBound(mItems) + 1
End Property

Public Property Get Item(ByVal Index As Long) As Variant '<- usually with Default-Attribute set
  Item = mItems(Index)
End Property
Public Property Let Item(ByVal Index As Long, RHS As Variant)
  mItems(Index) = RHS
End Property

Public Property Get Items() As Variant()
  Items = mItems
End Property

Public Function NewEnum() As IUnknown '<- needs Enumerable-ProcAttribute: -4
  Set NewEnum = New_c.EnumerateOn(Me, UBound(mItems) + 1)
End Function
Private Function IEnumerable_NextItem(Idx As Long) As Variant 'this is the IEnumerable-Callback
  IEnumerable_NextItem = mItems(Idx)
End Function

---

And Test-Form-Code again:

Code:

---

Private Sub Form_Load()
  Dim Arr As New Class1, V
      Arr.push 1
      Arr.push 2
      Arr.push 3
 
  Debug.Print "Arr-length: "; Arr.length
 
  For Each V In Arr.Items '<- but Items needs to be specified explicitely then
    Debug.Print V
  Next
 
  For Each V In Arr '<- now one can also directly enumerate on Arr
    Debug.Print V
  Next
End Sub

---

HTH

Olaf

---

The above two solutions are exactly what I need, especially the second solution using RC5.IEnumerable, which is perfect. Olaf, you are like a magician, you can always pull something amazing out of your hat. Much appreciated!

Quote:

---

Originally Posted by wqweto

http://www.vbforums.com/showthread.p...hout-a-typelib

Here is a "raw" implementation of a handy IEnumVARIANT light-weight object. It just forwards IEnumVARIANT::Next to parent object's default method with some code like this

VariantCopyToPtr rgVar, .Enumerable(.Index)

. . . so this trades the need to implement a custom IEnumerable interface for a bit of speed.

Of course RC5's solution is probably a lot more stable in the IDE as first it's a compiled DLL and second it's been excercised a bit more in the wild for some years now.

cheers,
</wqw>

---

Hi wqweto, the information you provided is very useful. At present, I'll use Olaf's method, and the DEXWERX's solution will be put into my database for future learning materials. Thank you very much, wqweto.

@Olaf: Just fiddled a bit with the RC5 enumerator impl and found that the following line brings the IDE down

Debug.Print TypeName(Arr.NewEnum)

While you at it investigating QI impl can you bolt a simple IDispatch tear-off object that handles DISPID_NEWENUM only so that this code works

Code:

---

  For Each V In Arr.NewEnum '<- has an IDispatch that returns itself on DISPID_NEWENUM
    Debug.Print V
  Next

---

The idea is for a dictionary replacement to be able to use separate enumerators for both keys and values like this

Code:

---

  For Each V In oDict.Keys
    Debug.Print "Key=" & V
  Next

  For Each V In oDict.Items
    Debug.Print "Item=" & V
  Next

  For Each V In oDict
    Debug.Print "Tuple=(" & V(0) & ", " & V(1) & ")"
  Next

---

cheers,
</wqw>

Quote:

---

Originally Posted by wqweto

Just fiddled a bit with the RC5 enumerator impl and found that the following line brings the IDE down
Debug.Print TypeName(Arr.NewEnum)

---

Thanks, should be fixed now, in new version 5.0.75
...(when you download - please re-register on your dev-machines despite being BinCompatible, because of new Interface- and Class-additions in RC5)

Quote:

---

Originally Posted by wqweto

While you at it investigating QI impl can you bolt a simple IDispatch tear-off object that handles DISPID_NEWENUM ...

---

Ok, done...
New version 5.0.75 now contains the complete functionality (+ a few extra-helpers) of what was shown here.
http://www.vbforums.com/showthread.p...BaseInterfaces
(the above line offers the Sources for a Dll which supports Base-Interface-SubClassing in a VB-Friendly manner).

An RC5-adapted Tutorial-Folder-Stack which demonstrates that functionality, is now available here:
Attachment 174621

For your outlined usecase, the Tutorial-Folder: 4 - MultiEnumerations per vbIEnumerable
should offer appropriate code...

@dreammanor
FWIW... cArrayList now got For Each support built-in as well...

HTH

Olaf

Nice work Olaf - There's been a couple of times I wished the cArrayList was enumerable, and now it is :)

Quote:

---

Originally Posted by Schmidt

For your outlined usecase, the Tutorial-Folder: 4 - MultiEnumerations per vbIEnumerable

---

Using vbIEnumerable now both

For Each V In Arr

. . . and

For Each V In Arr.NewEnum

. . . work. Great!

cheers,
</wqw>