ActiveX and VBA Developer's Guide > ActiveX Automation Basics > Collection Objects > 
Iterate through a Collection Object
 
 
 

To select a specific member of a Collection object, use the Item method. The Item method requires an identifier as either an index number specifying the location of the item within the collection or a string representing the name of the item.

The Item method is the default method for a collection. If you do not specify a method name when referring to a collection, Item is assumed. The following statements are equivalent:

ThisDrawing.Layers.Item("ABC")

ThisDrawing.Layers("ABC")
NoteDo not use the entity edit methods (Copy, Array, Mirror, and so forth) on any object while simultaneously iterating through a collection using the For Each mechanism. Either finish your iteration before you attempt to edit an object in the collection or create a temporary array and set it equal to the collection. Then you can iterate through the copied array and perform your edits.

Iteratethrough the Layers collection

The following example iterates through a collection and displays the names of all layers in the collection:

Sub Ch2_IterateLayer()

	' Iterate through the collection

	On Error Resume Next




	Dim I As Integer




	Dim msg As String




	msg = ""




	For I = 0 To ThisDrawing.Layers.count - 1




		msg = msg + ThisDrawing.Layers.Item(I).Name + vbCrLf




	Next




	MsgBox msg




End Sub










Find the
layer named MyLayer



The following
example refers to layer named MyLayer, and issues a message if the
layer does not exist:





Sub Ch2_FindLayer()




	' Use the Item method to find a layer named MyLayer




	On Error Resume Next







	Dim ABCLayer As AcadLayer




	Set ABCLayer = ThisDrawing.Layers("MyLayer")




	If Err <> 0 Then




		MsgBox "The layer 'MyLayer' does not exist."




	End If




End Sub