CODEWITHSUNDEEP
vbacollections
Marek
Marek

Reputation: 101

nested collections

Consider the following code:

Sub NestedCollections()
    Dim col1 As Collection
    Dim col2 As Collection
    Dim col3 As Collection

    Set col1 = New Collection
    Set col2 = New Collection
    Set col3 = New Collection

    col2.Add "a"
    col2.Add "b"
    col2.Add "c"

    col3.Add "d"
    col3.Add "e"
    col3.Add "f"

    col1.Add col2
    col1.Add col3

    col1.Item(2).Add col3

    Set col1 = Nothing
    Set col2 = Nothing
    Set col3 = Nothing
End Sub

If you add watch to "col1", and expand "item(2)", you'll notice that "item(4)" keeps on expanding. Why is this happening?

Cheers, Marek

Upvotes: 4

Views: 263

Answers (1)

Mathieu Guindon
Mathieu Guindon

Reputation: 71177

Everything works normally, up until col1.Item(2).Add col3 is executed.

Beyond that, col1.Item(2) is col3 as per this instruction:

col1.Add col3

By adding col3 to col1.Item(2), you're adding a pointer to col3 to... col3, which is why it "keeps expanding" - the 4th item of col3 is col3 itself:

col3.Add "d"   'col1.Item(2)(1)
col3.Add "e"   'col1.Item(2)(2)
col3.Add "f"   'col1.Item(2)(3)
col3.Add col3  'col1.Item(2)(4)

I wouldn't recommend using such a recursive data structure (i.e. adding a collection to itself).

Upvotes: 6

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