UserControl and a Collection as Property. How?

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ClarkVent - 28 May 2004 00:54 GMT

I'm creating a custom UserControl "MyControl" (in VB5/6). I want to have
a property "MyProp" like this:

MyControl.MyProp.Add
MyControl.MyProp(1).Text = "text"
MyControl.MyProp(1).Number = 0
MyControl.MyProp.Remove 1
etc...

Now I've searched quite a bit in the newsgroups and on the net in
general (and MS's MSDN), and all I could find so far is that this should
be solved with a Class Collection. However, nowhere could I find any
(code-) samples for this. Could anybody please direct me to a sample or
tutorial for this?

Thanks in advance.

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Steve Gerrard - 28 May 2004 03:35 GMT

> I'm creating a custom UserControl "MyControl" (in VB5/6). I want to have
> a property "MyProp" like this:
[quoted text clipped - 12 lines]
>
> Thanks in advance.

'class module CProp:

Option Explicit

Private mTxt As String
Private mNum As Double

Public Property Get Txt() As String
Txt = mTxt
End Property

Public Property Let Txt(RHS As String)
mTxt = RHS
End Property

Public Property Get Num() As Double
Num = mNum
End Property

Public Property Let Num(ByVal RHS As Double)
mNum = RHS
End Property

'user control MyControl:

Option Explicit

Private mCol As Collection

Private Sub UserControl_Initialize()
Set mCol = New Collection
End Sub

Public Function AddProp(Prop As CProp) As CProp
Call mCol.Add(Prop)
Set AddProp = Prop
End Function

Public Property Get Prop(IndexKey As Variant) As CProp
Set Prop = mCol.Item(IndexKey)
End Property

Public Sub RemoveProp(IndexKey As Variant)
Call mCol.Remove(IndexKey)
End Sub

Public Property Get PropCount() As Long
PropCount = mCol.Count
End Property

'Form1:

Private Sub Command1_Click()

With MyControl1

Call .AddProp(New CProp)

.Prop(1).Txt = "test"
.Prop(1).Num = 123
Debug.Print .Prop(1).Txt, .Prop(1).Num

.RemoveProp (1)

End With

End Sub

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ClarkVent - 30 May 2004 23:11 GMT

Thank you for your answer.

That's *almost* what I want. The difference being that your solution is
this:

MyControl1.AddProp(New CProp)
MyControl1.Prop(1).Txt = "test"
MyControl1.Prop(1).Num = 123
MyControl1.RemoveProp 1

and I need this:

MyControl1.Prop.Add <=== Different!
MyControl1.Prop(1).Txt = "test"
MyControl1.Prop(1).Num = 123
MyControl1.Prop.Remove 1 <=== Different!

reason being is that I need my control to be code-compatible with an
existing VB control. A lot of VB controls (like ListView, TreeView
TabStrip, etc) have collections as properties. The collection itself has
different properties/methods as the individual items. I figured out a
way to solve it (sort of) as follows:

Public Property Get Prop( Optional indexKey as Variant ) as Variant
If IsMissing(indexKey) Then
Set Prop = myCollection
Else
Set Prop = myCollection.Item(indexKey)
End If
End Property

The problem here is that this doesn't expose any of the
properties/methods at design time.

Thanks,

CV

>>I'm creating a custom UserControl "MyControl" (in VB5/6). I want to
>
[quoted text clipped - 89 lines]
>
> End Sub

Reply to this Message

Steve Gerrard - 31 May 2004 00:47 GMT

> Thank you for your answer.
>
[quoted text clipped - 12 lines]
> MyControl1.Prop(1).Num = 123
> MyControl1.Prop.Remove 1 <=== Different!

Ah, now I see what you are after. That can be done too. You need to
define a collection class, and use some procedure attributes to get the
effect you want. Here it goes:

'Class module CProp

' same as before

'Class module CPropList

Option Explicit

Private mCol As Collection

Private Sub Class_Initialize()
Set mCol = New Collection
End Sub

'use menu Tools / Procedure Attributes...
'click Advanced, and set the ProcedureID
'of the Item method to (Default)
'this allows the MyProp(1) syntax, which
'is really MyProp.Item(1)

Public Property Get Item(IndexKey As Variant) As CProp
Set Item = mCol.Item(IndexKey)
End Property

Public Sub Add()
mCol.Add New CProp
End Sub

Public Sub Remove(IndexKey As Variant)
mCol.Remove IndexKey
End Sub

'use menu Tools / Procedure Attributes...
'click Advanced, and set the ProcedureID
'of the NewEnum method to -4.
'this will enable use of the For Each syntax
'for iterating the collection

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

'user control MyControl:

Option Explicit

Private mPropList As CPropList

Private Sub UserControl_Initialize()
Set mPropList = New CPropList
End Sub

Public Property Get MyProp() As CPropList
Set MyProp = mPropList
End Property

'and then Form1:

Option Explicit

Private Sub Command1_Click()

With MyControl1

.MyProp.Add

.MyProp(1).Txt = "test"
.MyProp(1).Num = 123

Debug.Print .MyProp(1).Txt, .MyProp(1).Num

.MyProp.Remove 1

End With

End Sub

I personally prefer a more flexible Add method, one that returns the
object, and allows passing an object to be added, as I used in the first
example. Also, I would want to add an optional Key parameter, so the
collection could be built with keys, which are often faster than
indexes.

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ClarkVent - 31 May 2004 17:19 GMT

Perfect!!! That's *exactly* what I want! :)

Now why couldn't I find that anywhere on the net?

>>Thank you for your answer.
>>
[quoted text clipped - 102 lines]
> collection could be built with keys, which are often faster than
> indexes.

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VB Forum / General 2 / May 2004

UserControl and a Collection as Property. How?