changing size of 2D array with vba - arrays

Question

I always have trouble with Arrays which is why I usually avoid them but this time I'm trying to get my head round them
I'm trying to change the size of my Global Array inside vba
I have declared it using Public UseArr() As String
Now I've written a function that searches an SQL table and returns user information as a record set.
I want to take this record set and put it into my Global Array
This is the bit of code I've written for populating it
a = 0
If Not Not UseArr Then
For i = 0 To UBound(UseArr)
If StrComp(UseArr(i, 0), rs("Alias")) = 0 Then a = 1
Next i
b = i
Else
b = 0
End If
If a = 0 Then
ReDim Preserve UseArr(0 To b, 0 To 10)
With rs
If Not .BOF And Not .EOF Then
For j = 0 To 10
If Not rs(j) = "" Then
UseArr(b, j) = rs(j)
Else
UseArr(b, j) = "Null"
End If
Next j
End If
End With
End If
The idea being if the user is already in there it doesn't populate, and if not it populates.
It works fine for initialising the Array however when I go to put in a second user it throws a resize error.
Can anyone help?
Thanks in advance
Tom
Update with Dictionary Attempt
If UseList Is Nothing Then
Set UseList = New Dictionary
MsgBox "Created New"
End If
If UseList.Exists(rs("Alias")) Then
Dim temp()
For i = 0 To 10
temp(i) = rs(i + 1)
Next i
With UseList
.Add Key:=rs("Alias"), Item:=temp
End With
End If
Debug.Print UseList

Answer 1

You can only Redim Preserve the last dimension of a multi-dimensional array - see here. Have you considered using a Collection or Dictionary instead?
edit: using the code you've posted above, here's how you would display element 4 from the array associated with the key "tom"
MsgBox UseList("tom")(4)
or equivalently
MsgBox UseList.Item("tom")(4)

Answer 2

Here you have some explanation about how a Dictionary object works and some of its attributes and functions.
I think it's the best to reach your goal because they are so easy to use, fast and efficient.
First you have to import the mscorlib.dll into the Project References.
After you can use something like this to declare the dictionary:
Dim UseDict As Dictionary
Set UseDict = New Dictionary
To know if the Key you're searching is not in the Dictionary and then add the new user:
If Not UseDict.Exists(Key) Then
UseDict.Item(Key) = 1
End If
The Value is not important here, but if you wanted to count how many times a key appears somewhere, you could increment the value when UseDict.Exists(Key) = True.
That's what the Dictionaries, Hash-maps or Maps stand for: count and search efficiently.
Hope it helps!

Answer 3

I attach a code with some corrections. I think the problem is that you are trying to access to an array as if it was a variable. That means you have to loop through the item of a key.
I add comments to the code below:
Update
If UseList Is Nothing Then
Set UseList = New Dictionary
MsgBox "Created New"
End If
If UseList.Exists(rs("Alias")) Then
'i think is better to specify the data type and the dimension.
Dim temp(10) as string
'if you loop from 0 to 10 the array will have 11 elements
For i = 0 To 9
temp(i) = rs(i + 1)
Next i
'This will work also and looks nicer (in my opinion) than the method
'you pasted, but if that worked anyway don't change it ;)
UseList(rs("Alias")).Item = temp
End If
Now, if you want to retrieve the result you must:
For i = 0 To UBound(UseList.Item(rs("Alias")) - 1
Debug.Print UseList.Item(rs("Alias"))(i)
Next i
Give me feedback when you test the code, please :)