Visual Basic Programming Code Examples

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Determine if an item exists in a collection



Determine if an item exists in a collection

The following code shows you how to determine if an item exists within a collection.

Option Explicit

'Purpose     :  Determines if an item already exists in a collection
'Inputs      :  oCollection         The collection to test for the existance of the item
'               vIndex              The index of the item.
'               [vItem]             See Outputs
'Outputs     :  Returns True if the item already exists in the collection.
'               [vItem] The value of the item, if it exists, else returns "empty".
'Notes       :
'Example     :

Function CollectionItemExists(vIndex As Variant, oCollection As Collection, Optional vItem As Variant) As Boolean
    On Error GoTo ErrNotExist
    
    'Clear output result
    If IsObject(vItem) Then
        Set vItem = Nothing
    Else
        vItem = Empty
    End If
    
    If VarType(vIndex) = vbString Then
        'Test if item exists
        If VarType(oCollection.Item(CStr(vIndex))) = vbObject Then
            'Return an object
            Set vItem = oCollection.Item(CStr(vIndex))
        Else
            'Return an standard variable
            vItem = oCollection.Item(CStr(vIndex))
        End If
    Else
        'Test if item exists
        If VarType(oCollection.Item(Int(vIndex))) = vbObject Then
            'Return an object
            Set vItem = oCollection.Item(Int(vIndex))
        Else
            'Return an standard variable
            vItem = oCollection.Item(Int(vIndex))
        End If
    End If
    'Return success
    CollectionItemExists = True
    Exit Function
ErrNotExist:
    CollectionItemExists = False
    On Error GoTo 0
End Function

'Demonstration routine
Sub Test()
    Dim oColl As New Collection, oValue As Variant
    
    oColl.Add "red1", "KEYA"
    oColl.Add "red2", "KEYB"
    'Return the two items in the collection
    Debug.Print CollectionItemExists("KEYA", oColl, oValue)
    Debug.Print "Returned: " & oValue
    Debug.Print "-----------"
    Debug.Print CollectionItemExists(2, oColl, oValue)
    Debug.Print "Returned: " & oValue
    'Should fail
    Debug.Print CollectionItemExists("KEYC", oColl, oValue)
    Debug.Print "Returned: " & oValue
    Set oColl = Nothing
End Sub