VBA - How Can I Get Randomize String Array To Work? - ms-access

Question

Overview: I am pasting many words on separate lines into text box: txtWordRandomizer. Then, move each line into the string array. I need to shuffle/randomize the array, but can't seem to get it to work.
I got the bottom Sub, ShuffleArray(), here: http://www.cpearson.com/excel/ShuffleArray.aspx
...and it seems to be what everyone references when talking about shuffling/randomizing an array.
I get Error: Type Mismatch: array or user-defined type expected on calling ShuffleArrayInPlace(), but thought this was for randomizing a string array. Do I somehow need to translate the string array into a variant array?
Or, any other suggestion on how I can get this to work?
Private Sub btnRandomize_Click()
Dim strRandoms() As String
strRandoms() = Split(Me.txtWordRandomizer.Value, vbCrLf)
strRandoms() = ShuffleArray(strRandoms())
End Sub
Function ShuffleArray(InArray() As Variant) As Variant()
' This function returns the values of InArray in random order. The original
' InArray is not modified.
Dim N As Long
Dim Temp As Variant
Dim J As Long
Dim Arr() As Variant
Randomize
L = UBound(InArray) - LBound(InArray) + 1
ReDim Arr(LBound(InArray) To UBound(InArray))
For N = LBound(InArray) To UBound(InArray)
Arr(N) = InArray(N)
Next N
For N = LBound(InArray) To UBound(InArray)
J = CLng(((UBound(InArray) - N) * Rnd) + N)
Temp = InArray(N)
InArray(N) = InArray(J)
InArray(J) = Temp
Next N
ShuffleArray = Arr
End Function

Answer 1

Based on some quick testing, the ShuffleArray function in the posted link doesn't actually return a randomized array. Since you're keeping your array in the strRandoms variable, you can use the in-place function anyways (the in-place function will also be more efficient, since it doesn't have to create and populate an entirely new array when called).
When calling the function and passing your array as an argument, don't include parentheses after your array. So do this:
ShuffleArrayInPlace a
' Or this:
Call ShuffleArrayInPlace(a)
However, in order to do this successfully, you have to slightly change the method signature of ShuffleArrayInPlace from this (as it is now):
Sub ShuffleArrayInPlace(InArray() As Variant)
to this:
Sub ShuffleArrayInPlace(InArray As Variant)
Note that the parentheses after the InArray are gone. Why do this?
Originally, with the parentheses, the function is expecting an array of Variant values. However, the split function returns an array of string values. By changing the method signature to remove the parentheses, you're basically saying you can pass anything to the function (a string array, a variant array, or even something that's not an array at all). Because of this, you could update ShuffleArrayInPlace to raise an error if the argument is not an array (using the IsArray function).
Speaking of refactoring: While the algorithm the ShuffleArrayInPlace uses to shuffle an array is clear, it's not necessarily the best one. I would review the Fisher-Yates shuffle, and try implementing it yourself in VBA as an exercise.
So, in summary...
When calling a function that takes an array as an argument, don't put parentheses after the array: `Call ShuffleArrayInPlace(strRandoms)
Use ShuffleArrayInPlace, not ShuffleArray.
Change the ShuffleArrayInPlace function so that InArray is a Variant, not Variant().

Answer 2

This works for me:
Private Sub btnRandomize_Click()
Dim strRandoms() As String
strRandoms = Split("A|B|C|D|E", "|")
strRandoms = ShuffleArray(strRandoms)
Debug.Print Join(strRandoms, ", ")
End Sub
Function ShuffleArray(InArray() As String) As String()
Dim N As Long, Temp As Variant
Dim J As Long, Arr() As String
Randomize
'make a copy of the array
ReDim Arr(LBound(InArray) To UBound(InArray))
For N = LBound(InArray) To UBound(InArray)
Arr(N) = InArray(N)
Next N
'shuffle the copy
For N = LBound(Arr) To UBound(Arr)
J = CLng(((UBound(Arr) - N) * Rnd) + N)
Temp = Arr(N)
Arr(N) = Arr(J)
Arr(J) = Temp
Next N
ShuffleArray = Arr 'return the shuffled copy
End Function