solve mismatch error for visual basic 6.0 - arrays

Question

When I run this code it show a dialog box that says 'Mismatch Type' at line For i = 0 To UBound(arffArray). What is the problem with my code?
Public Function processFile()
Dim i, j, posRelation, temp, att, data, flag
Dim strRelation
Dim strAtt
Dim strData
strRelation = "#relation"
strAtt = "#attribute"
strData = "#data"
att = 0
data = 0
For i = 0 To UBound(arffArray)
If (InStr(arffArray(i), strRelation)) Then
temp = Replace(Mid(arffArray(i), 11, Len(arffArray(i))), "'", "")
RelationName = temp
ElseIf (InStr(arffArray(i), strAtt)) Then
flag = parseAtt(att, arffArray(i))
If (Not flag) Then
processFile = flag
Exit Function
End If
att = att + 1
ElseIf (InStr(arffArray(i), strData)) Then
data = readTheRest(i)
i = UBound(arffArray) 'end the loop
totalData = data
End If
Next
'get the list of class name
Dim tmpClassAttr
tmpClassAttr = attArray(1, UBound(attArray, 2))
For i = 0 To UBound(tmpClassAttr)
ReDim Preserve classArray(i)
classArray(i) = Trim(tmpClassAttr(i))
Next
processFile = True
End Function
'------------------------------------------------------------
'Function: parseAtt(num, attrData, ByVal m As MineKnow)
'require:
' >#num -> current attribute counter
' >#attrData -> current attribute declaration
'Raises: error if reading non numeric data/attribute
'Return: boolean parseAtt TRUE/FALSE, TRUE if parse successfully or otherwise
'Effect: parsing file content to:
' > attributes
'------------------------------------------------------------
Private Function parseAtt(num, attrData)
Dim temp, i, j, strAtt, temp2, pos, atVal
ReDim Preserve attArray(2, num)
'possible type of declarations
'#attribute outlook {sunny, rainy, overcast}
'#attribute outlook {sunny,rainy,overcast}
'attribute pos = 12
'get the attribute name first get the pos of "{"
pos = InStr(1, attrData, "{", 1)
If (pos = 0) Then
error = "---->Nominal attribute only." & vbCrLf & "---->" & attrData
parseAtt = False
Exit Function
Else
strAtt = Trim(Mid(attrData, 12, pos - 12))
atVal = Mid(attrData, pos + 1, Len(attrData) - (pos + 1))
atVal = Replace(atVal, "'", "")
atVal = Replace(atVal, "''", "")
atVal = Replace(atVal, "}", "")
atVal = Replace(atVal, " ", "")
temp = Split(atVal, ",")
attArray(0, num) = strAtt
attArray(1, num) = temp
parseAtt = True
End If
End Function

Answer 1

The biggest problem with your code is that you don't declare the type of your variables!!
Statements like
Dim i
will just declare the variable i as type Variant, which is definitely not what you want.
You actually want i to be declared as an Integer. You accomplish that by explicitly specifying the type at the point of declaration:
Dim i As Integer
Since the For loop is expecting an iterator index variable with type Integer, this should stop it from choking up that error.
Likewise, strings should always be declared explicitly as String types:
Dim strRelation As String
Note that when you declare multiple variables on a single line (which you probably shouldn't do, for clarity reasons), you need to make sure that you specify the type for each variable. It is not cumulative like other languages.
For example, this statement
Dim i, j, k As Integer
will declare only k as an Integer. i and j will be of type Variant, which is almost certainly (again) not what you wanted.
Instead, you need to write
Dim i As Integer, j As Integer, k As Integer
Of course, in this particular case, since VB 6 allows you to use variables with a lower bound that is not 0, it's probably best to code the loop like this:
Dim i As Integer
For i = LBound(arffArray) To UBound(arffArray)
' Do something with the array
Next i