VBA - Create Dynamic Variable from different strings - vba

Question

I'm a beginner on VBA. I have been following SO for years but have never really posted. I'm really struggling to understand a concept and have found no answers elsewhere.I want to use a for loop that 's going to loop these three arrays going like the following:
EUR_Buy = (1,2,3,4,5,6)
USD_BUY = (2,4,6,8,10,12)
GBP_BUY = (1,3,5,7,9,11)
curr = (EUR,USD,GBP)
For i = 0 To 2
For j = 0 To 5
If curr(i) & "_BUY" & (j) = 8
MsgBox Yes
End If
Next j
Next i
The only thing I get is the name of the variable (ex: Eur_Buy(0) but not the value of the value which would be "1". Any idea how I could get this? Would be very helpful).
Thanks a lot and please do not hesitate if you have any questions.

Answer 1

You cannot create a string from pieces and then expect the runtime to use this as variable name.
If you have a list of names and associated values, you can use a Collection (or a Dictionary).
The following piece of code gives you the idea how to use them.
' Create collection and fill it with 3 elements, each holding an array of 6 values
Dim myVars As New Collection
' Elements are added to a collection with add <value>, <key>
myVars.Add Array(1, 2, 3, 4, 5, 6), "EUR_Buy"
myVars.Add Array(2, 4, 6, 8, 10, 12), "USD_BUY"
myVars.Add Array(1, 3, 5, 7, 9, 11), "GBP_BUY"
Dim curr as Variant
Dim j As Long
For Each curr In Array("EUR", "USD", "GBP")
Dim key As String
key = curr & "_BUY"
' You can access an element of a collection with it's key (name) or index.
For j = 0 To 5
If myVars(key)(j) = 5 Then Debug.Print curr, j, "Found 8 in " & key
Next
Next

Answer 2

Referencing an Array of arrays via Enum statement
If you have to deal with a greater number of currencies, it can increase readibility to
use an enumeration defined in the head of a code module and to
reference an Array of arrays (aka jagged array) by these placeholder variables in the main code and which
holds the individual currency arrays for its part; you may think it as sort of container.
Option Explicit ' head of code module
Enum C ' Enum statement allows automatic increments (if no special assignments)
[_Start] = -1
EUR
USD
GBP
LastElement = GBP ' (re-)set to last currency (here GBP), if changed
End Enum
Note that you can easily insert or add other currencies without caring in further code for the actual number as Enum automatically increments the start element (if not assigned explicitly).
The following example code
assigns the individual arrays (starting a little bit tricky with the "Name" of the array as string value, e.g. "EUR") to buy() serving as container array and
executes a Match over all enumerated currencies eventually.
Sub ExampleCall()
'1) define zero-based buy arrays referenced by Enum values (~> module top)
Dim buy(C.LastElement) ' declare 0-based Array of arrays
buy(C.EUR) = Array("EUR", 1, 2, 3, 4, 5, 6) ' assign the individual arrays
buy(C.USD) = Array("USD", 2, 4, 6, 8, 10, 12)
buy(C.GBP) = Array("GBP", 1, 3, 5, 7, 9, 11)
'2) define a search value
Dim srch As Variant
srch = 5
'3) find value 5
Dim curr As Long
For curr = 0 To C.LastElement
Dim no As Variant
no = Application.Match(srch, buy(curr), 0) ' << Find ordinal element position
If IsNumeric(no) Then ' check for valid findings only
no = no - 1 ' adjust counter as Match returns 1-based numbers
'4) display result of individual sub-array buy(curr)
Debug.Print _
buy(curr)(0), _
"index " & no, _
"Found " & buy(curr)(no) & " in " & buy(curr)(0) & "_BUY"
End If
Next
End Sub
Note that Application.Match always returns a 1-based position number (adjusted to the 0-based index by a -1 subtraction) within the individual arrays or an Error if there is no finding at all; checking the no result by IsNumeric allows to get only valid findings.
Results in the VB Editor's immediate window would be displayed e.g. as follows:
EUR index 5 Found 5 in EUR_BUY
GBP index 3 Found 5 in GBP_BUY