How to get VBA Subroutine to call a function that passes an array to another function within the subroutine

Question

I am trying to get my VBA subroutine to run a function that creates an array and then passes that array to another function which further processes those array items. I have made an example that is extremely simple and functions exactly like my actual code. it is as follows:

Sub SubRoutine()
ProcessArray CreateArray
End Sub
Function ProcessArray(Arr() As Variant) As Variant
End Function
Function CreateArray() As Variant
Dim Array1(1 To 4) As Variant
CreateArray = Array1
End Function

It's just the two functions and the subroutine which calls those two functions. The compiler refuses to compile my code and explains to me that:

Compile error:

Type mismatch: array or user-defined type expected

To which I can only say that everything is the same data type and the argument passed is indeed an array. Just in case you were wondering, yes I have tried with an array that has had data allocated to it.

I know it's something subtle I am missing in VBA syntax but I have not seen an example like this. Any insight would be greatly appreciated.

Answer 1

Change this line:
Function ProcessArray(Arr() As Variant) As Variant
to this:
Function ProcessArray(Arr As Variant) As Variant

This way your function will now accept a Variant that contains an array, instead of looking for an array of Variants. As you said, a subtle but significant difference.

Answer 2

I think what still wasn't answered is why
1. MySub(MyArg)
works just fine, but
2. MyOtherSub(MyArg1, MyArg2)
does not

This blog entry explains it well.

Essentially, you can pass an argument which would normally be byref as byval:
Call MySub(Arg1, (Arg2)) 'Arg1 is passed byref, Arg2 is passed byval

Code #1. works because VBA thinks you are passing one argument byVal so it doesnt count as parentheses being used in a Sub call without the Call keyword. As mentioned in other answers, no parentheses are allowed in a Sub call without the Call keyword.

The Call keyword requires Params in parentheses. So with the Call keyword Call MySub(MyArg) would actually pass MyArg byRef because the parentheses are used as the enclosure for arguments.

Code #2 does not work because there is no valid way to justify the parentheses in the syntax (it is only allowed with the Call keyword.