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VBA - classes and structures videos | Excel VBA Part 37 - Custom Collections

Posted by Andrew Gould on 27 October 2014

Excel VBA Part 37 - Custom Collections

Excel VBA is full of collections and you can even create your own custom collections using the Collection object. This video teaches you how to create a new custom collection, how to add items to it, how to reference those items individually and how to loop over all of the items in the collection. You'll also see how you can add items based on a custom class module to a collection.

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From:	duggie
When:	29 Jan 22 at 14:14

Reply to duggie

I came across this code from another website:

These lines are in the class collectionExt:

Public Function Clone() As collectionExt

Dim newColl As New collectionExt

' some more code

End Function

It seems inside the function, it is decalring an instance of itself. How come it's not recursive?

From:	Andrew G
When:	31 Jan 22 at 15:46

Reply to Andrew G

Hi duggie!

It would be recursive if the Clone function called itself. Or if the Initialize event of the class called the Clone function. Or if the Initialize event of the class created a new instance of itself.

As it is, the Clone function creates one new instance of the class each time the Clone function is called.

I hope it helps!

From:	duggie
When:	31 Jan 22 at 15:48

Reply to duggie

Andrew,

Thanks for explaining. Wasn't sure initially what you meant by the "Zone" function but then I realised it must've been a typo.

From:	Andrew G
When:	31 Jan 22 at 19:20

Reply to Andrew G

Oops! Yes, my mistake, I've corrected it now, thanks for pointing it out!

From:	duggie
When:	20 Sep 18 at 21:44

Reply to duggie

This code removes all rows if column E contains Oranges

but I've had to declare a large SubArray, as big as the original array.

ReDim SubArray(1 To DataArrayRows, 1 To DataArrayCols) As Variant

Is it possible to use collections to "add-on-the-fly"?

Dim DataArray() As Variant

    DataArray() = Sheet1.Cells(1, 1).CurrentRegion.Value

    Dim DataArrayRows As Long

    DataArrayRows = UBound(DataArray(), 1)

    Dim DataArrayCols As Long

    DataArrayCols = UBound(DataArray(), 2)

    Dim SubArray() As Variant

    ReDim SubArray(1 To DataArrayRows, 1 To DataArrayCols) As Variant

    Dim I As Long, j As Long, k As Long

    j = 1

    k = 1

    Dim Coll1 As Collection
    Dim Coll2 As Collection
    Dim Coll3 As Collection
    Dim Coll4 As Collection
    Dim Coll5 As Collection
    Dim Coll6 As Collection
    Dim Coll7 As Collection
    Dim Coll8 As Collection
    Dim Coll9 As Collection
    Dim Coll10 As Collection
    Set Coll1 = New Collection
    Set Coll2 = New Collection
    Set Coll3 = New Collection
    Set Coll4 = New Collection
    Set Coll5 = New Collection
    Set Coll6 = New Collection
    Set Coll7 = New Collection
    Set Coll8 = New Collection
    Set Coll9 = New Collection

    Set Coll10 = New Collection
    For i = 2 To DataArrayCols

        If DataArray(i, 12) <> "RD" Then

            Coll1.Add DataArray(i, 1)
            Coll2.Add DataArray(i, 2)
            Coll3.Add DataArray(i, 3)
            Coll4.Add DataArray(i, 4)
            Coll5.Add DataArray(i, 5)
            Coll6.Add DataArray(i, 6)
            Coll7.Add DataArray(i, 7)
            Coll8.Add DataArray(i, 8)
            Coll9.Add DataArray(i, 9)
            Coll10.Add DataArray(i, 10)

            k = k + 1

        End If

    Next i

    Sheet3.Cells(2, 1).Resize(k - 1, DataArrayCols).Value = SubArray()

but it seems cumbersome.

How can I use a collection without having to declare it many times?

From:	Andrew G
When:	21 Sep 18 at 09:12

Reply to Andrew G

I don't think that a collection will help you here. Regardless of how you populate it, you won't be able to write its contents into a range of cells in a single step in the same way you can with an array. You would have to loop over the collection after you have populated it and write out its contents one-by-one.

For the sake of interest, you could use a single collection as shown below:

Sub PopulateCollection()

Dim DataArray
Dim DataArrayRows As Long
Dim DataArrayCols As Long

Dim i As Long, j As Long
Dim Coll1 As Collection

DataArray = Sheet1.Cells(1, 1).CurrentRegion
DataArrayRows = UBound(DataArray, 1)
DataArrayCols = UBound(DataArray, 2)

Set Coll1 = New Collection

'Loop through array and add matching values to collection
For i = 2 To DataArrayRows
If DataArray(i, 12) <> "RD" Then
For j = 1 To DataArrayCols

Coll1.Add Item:=DataArray(i, j)

Next j
End If
Next i

'Loop through collection and list its values
Dim v As Variant

For Each v In Coll1
Debug.Print v
Next v

End Sub

You may also be interested in this post which talks about ways to create a key for each item in the collection https://stackoverflow.com/questions/5702362/vba-collection-list-of-keys

I hope that helps!

From:	duggie
When:	22 Sep 18 at 07:14

Reply to duggie

Thanks, greatly appreciated.

From:	Andrew G
When:	24 Sep 18 at 09:09

Reply to Andrew G

No problem!

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