byref Type Mismatch Error when declaring multiple variables in single row

[szilvia_vf]

Hi!

I guess I would need a bit of explanation what actually happens when I declare variables in a single row. If I do so, passing the variable to another Sub in the default ByRef method won't work. I know two possible solutions (workarounds?) for my issue, but I want to understand why it works, and why the original approach does not.

Here is a short code that gives byref type mismatch error when trying to compile:

Sub Macro1()

   Dim A, B As Integer
   A = 50
   B = 10
   Macro2 A
   Debug.Print A

End Sub

Sub Macro2(ByRef A As Intger)
    A = A * 10
End Sub

 One solution is to declare A and B variables in different rows, like this:

   Dim A As Integer
   Dim B As Integer

Another solution is if I pass the value of the variable instead of the reference in Macro2, but in that case A won't get the new value:

Sub Macro2(ByVal A As Integer)
    A = A * 10
End Sub

I would like to understand why? What happens when I declare the variables at once that prevents the project to get compiled?

Thanks for the explanation!

[#2 · Accepted solution]

@szilvia_vf 

Unlike most other programming languages, VBA requires that you specify each variable's data type separately when you declare them on a single line. If you don't, they are declared as the default type Variant.

So

    Dim A, B As Integer

is equivalent to

    Dim A As Variant, B As Integer

When you call Macro2, the argument that you pass to the ByRef argument A must be Integer (I assume that Intger was a typo). Since A is effectively declared as Variant in the line above, you get a Type Mismatch error.

Solution:

    Dim A As Integer, B As Integer

In this version, both A and B are declared explicitly as Integer.

[#3]

I learn something new every day. In this case I had an inappropriate declaration habit so far. Thank you! (indeed, Intger was just a typo)