Collection object

A Collection object is an ordered set of items that can be referred to as a unit.


The Collection object provides a convenient way to refer to a related group of items as a single object. The items, or members, in a collection need only be related by the fact that they exist in the collection. Members of a collection don't have to share the same data type.

A collection can be created the same way other objects are created. For example:

Dim X As New Collection

After a collection is created, members can be added by using the Add method and removed by using the Remove method. Specific members can be returned from the collection by using the Item method, while the entire collection can be iterated by using the For Each...Next statement.


This example creates a Collection object (MyClasses), and then creates a dialog box in which users can add objects to the collection.

To see how this works, choose the Class Module command from the Insert menu and declare a public variable called InstanceName at the module level of Class1 (type Public InstanceName) to hold the names of each instance. Leave the default name as Class1. Copy and paste the following code into the General section of another module, and then start it with the statement ClassNamer in another procedure.

(This example only works with host applications that support classes.)

Sub ClassNamer()
    Dim MyClasses As New Collection    ' Create a Collection object.
    Dim Num    ' Counter for individualizing keys.
    Dim Msg As String    ' Variable to hold prompt string.
    Dim TheName, MyObject, NameList    ' Variants to hold information.
        Dim Inst As New Class1    ' Create a new instance of Class1.
        Num = Num + 1    ' Increment Num, then get a name.
        Msg = "Please enter a name for this object." & vbNewLine _
         & "Press Cancel to see names in collection."
        TheName = InputBox(Msg, "Name the Collection Items")
        Inst.InstanceName = TheName    ' Put name in object instance.
        ' If user entered name, add it to the collection.
        If Inst.InstanceName <> "" Then
            ' Add the named object to the collection.
            MyClasses.Add item := Inst, key := CStr(Num)
        End If
        ' Clear the current reference in preparation for next one.
        Set Inst = Nothing
    Loop Until TheName = ""
    For Each MyObject In MyClasses    ' Create list of names.
        NameList = NameList & MyObject.InstanceName & vbNewLine
    Next MyObject
    ' Display the list of names in a message box.
    MsgBox NameList, , "Instance Names In MyClasses Collection"

    For Num = 1 To MyClasses.Count    ' Remove name from the collection.
        MyClasses.Remove 1    ' Since collections are reindexed automatically, remove the first member on each iteration.
End Sub

See also

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