I don't like variants but...

[brzak]

Form what i hear / read, there are many reasons not to use a variant.
I've found couple of nice uses for it though and would like to get
some feedback on what other people think.

One example i would have thought where it's use would be allowable
would be if there is a case where a loop through a group is required
that does not follow any simple pattern.

Say four of the seven days in the week required traversing:

Sub Using_Variant()
Dim Day As Variant
For Each Day In Array("Monday", "Wednesday", "Saturday",
"Sunday")
Debug.Print Day
Next Day
End Sub

seems tidier than:

Sub Without_Using_Variant()
Dim Day(1 To 4) As String
Dim n As Integer
Day(1) = "Monday"
Day(2) = "Wednesday"
Day(3) = "Saturday"
Day(4) = "Sunday"
For n = LBound(Day) To UBound(Day)
Debug.Print Day(n)
Next n
End Sub


I'd be interested to see what other more experienced people might
think.

What is the point of a variant? It must exist to serve some purpose?
To me it seems a bit lazy to use it, as you should know what you want
- is it to overcome incompatibilities between the existing data types?

And getting back to the above example, if the day name was used
extensively, even though the variant takes a string and has type
Variant/String - would the loss in performace mean that those extra
few lines at the start would be worth it.

The second option would be more attractive if it were possible to do
this:

Dim Day(1 to 4) as String
Day() = Array("Monday", "Wednesday", "Saturday", "Sunday")

but no, the number of lines taken up is dictated by the number of
elements in the array...

Thanks for listening1

 

[Charles Williams]

Although using variants is slower and uses more memory than using more
tightly defined datatypes most of the time you will not notice any speed
difference.

The major reason for using Variants is that an Excel cell, like a variant,
can contain many different kinds of data (Empty, string, double, Error,
boolean etc), and is often the result of a formula that can return multiple
datatypes (double or error for instance).

So it is simpler and more efficient to get the values from a range of Excel
cells into a variant rather than try to handle the cells one by one and
determine their datatypes and then put them into the appropriate VBA
variable.


Charles
__________________________________________________
The Excel Calculation Site
http://www.decisionmodels.com

 

[brzak]

Hi Charles,

Yes, that's the main thing I use them for, in fact the microsoft blog
on excel recently posted a comparison of the various methods of
dealing with data on the worksheet, they have some nice tables showing
differences in time. that's here:

http://blogs.msdn.com/excel/archive...stest-way-to-scan-a-large-range-in-excel.aspx

What about in the example i posted - what would your approach be
there?

Thanks

Nice website btw

 

[Jim Thomlinson]

Your example is a perfectly reasonable use of variant. Variants are a very
powerful feature of VBA. In some other languages that don't have variants you
end up doing a lot of work to get around the data type issue. For example if
you want a numeric input from your user (who could enter enaything) you end
up storing the input in a string and then having to validate the string to be
numeric and then coerce the value to a number.

The problem with variants is that they tend to be overused. If you can
reasonably know the data type of the variable you should explicitly define it
that way. It is more efficient but more importantly it is going to make your
life easier. If you try to pass a string into a double you will get a simple
error message letting you know that there is a problem. If you want a range
object then if you define it as type range you will get intellisence drop
downs when you use the variable.

 

[Rick Rothstein]

You could always do your loop either of these ways without needing a Variant
variable...

For X = 0 To 3 ' for Option Base 0; 1 To 4 for Option Base 1
Print Array("Monday", "Wednesday", "Saturday", "Sunday")(X)
Next

For X = 0 To 3 ' Split always returns a zero-based array
Print Split("Monday Wednesday Saturday Sunday")(X)
Next

Although that last one would be slightly more efficient if done this way...

Dim Days() As String
Days = Split("Monday Wednesday Saturday Sunday")
For X = 0 To 3 ' although you can use UBound(Days) if unsure of how many
elements
Print Days(X)
Next

 

[brzak]

Thanks Rick,

That's one less place I need to use the variant type. That last
example is probably the one I would most favour, only one extra line
of code my original variant example, but a lot clearer.

I agree Jim, I've also seen it overused, can make it messy and
unnecessarily slow.

One other interesting use of the variant that has been as a method to
work out the type of something.

That's instead of trawling through the sometimes unnavigable help file
- would be nice if search functionality was improved so taht you could
"Windows-Live-search" it... or not

 

[Rick Rothstein]

Oh, I forgot one other possibility you can make use of. If you do not have a
long list of items, you can also use the Choose function...

Dim X As Long
For X = 1 To 4
Debug.Print Choose(X, "Monday", "Wednesday", "Saturday", "Sunday")
Next

--
Rick (MVP - Excel)



Thanks Rick,

That's one less place I need to use the variant type. That last
example is probably the one I would most favour, only one extra line
of code my original variant example, but a lot clearer.

I agree Jim, I've also seen it overused, can make it messy and
unnecessarily slow.

One other interesting use of the variant that has been as a method to
work out the type of something.

That's instead of trawling through the sometimes unnavigable help file
- would be nice if search functionality was improved so taht you could
"Windows-Live-search" it... or not