How do I traverse a collection in classic ASP?

Question

I want to be able to do:

For Each thing In things
End For

CLASSIC ASP - NOT .NET!

Answer 1

Whatever your [things] are need to be written outside of VBScript.

In VB6, you can write a Custom Collection class, then you'll need to compile to an ActiveX DLL and register it on your webserver to access it.

Answer 2

Something like this?

dim cars(2),x
cars(0)="Volvo"
cars(1)="Saab"
cars(2)="BMW"

For Each x in cars
  response.write(x & "<br />")
Next

See www.w3schools.com.

If you want to associate keys and values use a dictionary object instead:

Dim objDictionary
Set objDictionary = CreateObject("Scripting.Dictionary")
objDictionary.Add "Name", "Scott"
objDictionary.Add "Age", "20"
if objDictionary.Exists("Name") then
    ' Do something
else
    ' Do something else 
end if

Answer 3

The closest you are going to get is using a Dictionary (as mentioned by Pacifika)

Dim objDictionary
Set objDictionary = CreateObject("Scripting.Dictionary")
objDictionary.CompareMode = vbTextCompare 'makes the keys case insensitive'
objDictionary.Add "Name", "Scott"
objDictionary.Add "Age", "20"

But I loop through my dictionaries like a collection

For Each Entry In objDictionary
  Response.write objDictionary(Entry) & "<br />"
Next

You can loop through the entire dictionary this way writing out the values which would look like this:

Scott
20

You can also do this

For Each Entry In objDictionary
  Response.write Entry & ": " & objDictionary(Entry) & "<br />"
Next

Which would produce

 Name: Scott
 Age: 20

Answer 4

One approach I've used before is to use a property of the collection that returns an array, which can be iterated over.

Class MyCollection
    Public Property Get Items
        Items = ReturnItemsAsAnArray()
    End Property
    ...
End Class

Iterate like:

Set things = New MyCollection
For Each thing in things.Items
    ...
Next

Answer 5

As Brett said, its better to use a vb component to create collections. Dictionary objects are not very commonly used in ASP unless for specific need based applications.

Answer 6

Be VERY carefully on using VB Script Dictionary Object!
Just discover this "autovivication" thing, native on this object: http://en.wikipedia.org/wiki/Autovivification

So, when you need to compare values, NEVER use a boolen comparison like:
If objDic.Item("varName") <> "" Then...
This will automatically add the key "varName" to the dictionary (if it doesn't exist, with an empty value) , in order to carry on evaluating the boolean expression.

If needed, use instead If objDic.Exists("varName").

Just spend a few days knocking walls, with this Mcrosoft "feature"...
vbscript-dictionary-object-creating-a-key-which-never-existed-but-present-in-another-object