Declaring variables

[chuckles1066]

Just posting on from something I read earlier.

Dim a, b, c, d as Integer

Only d is given the type integer in this example whereas I assumed a, b and c would also be type integer?

So what type are a, b and c?

I'm a bit concerned because, obviously, my misunderstanding might have adverse or unpredictable consequences in some of the macros I've written.

TIA.

 

[shg]

Variables whose data types are not specified are Variants.

 

[VoG]

That declares a, b and c as Variant and d as Integer. You should use

Dim a As Integer, b As Integer, c As Integer, d As Integer

 

[chuckles1066]

Thanks both.

So, stating the bleeding obvious (as Basil Fawlty would say)

Dim a, b, c, d, e as Boolean

is going to cause someone a lot of grief if a, b, c and d are only ever intended to be True or False?

 

[shg]

A Variant can contain anything, so it's not going to intrinsically cause a problem, but it's sloppy practice to not strongly type most variables. If you need a Variant (and sometimes you will), declare the variable as a Variant.

There's an option in the VBE (Tools > Options) to require variable declaration. You should tick it.

 

[kpark91]

You should always put

Option Explicit

at the top of your module to make sure you declare all your variables (as it will allow your code to be faster if explicitly stated)

Moreover, to not tire your fingers, you can use variable identifiers such as %,&, #, $.

This will allow your code to appear much shorter and easier to read (imo)

VARIABLE IDENTIFIER
Interger = %
Long = &
Currency = @
Single = !
Double = #
String = $

So, you would use them like this

Dim a%, b%, c%, d%

to declare as integers.

 

[shg]

I would not declare variables like that (using type declaration characters) unless my disk drive had less than 5MB of storage.

 

[kpark91]

shg, may I ask why not?
I have just found out about the type declaration characters and do not know the drawbacks of them or the advantages as a matter of fact..

 

[shg]

Computers execute code, but only people read it. Code should be written to be easy to understand.

Declaring variables also affords the opportunity to explain usage:

Function AlignKeys1(wks As Worksheet) As Boolean
    Dim rKey        As Range    ' cells in header row containing the first column of each dataset
    Dim cell        As Range    ' For Each loop control variable
 
    Dim iRow        As Long     ' row index
    Dim iCol        As Long     ' column index
    Dim aiCol()     As Long     ' array containing the column indices of Keys
 
    Dim ar()        As Range    ' an array of ranges containing each of the datasets to be aligned
    Dim iRng        As Long     ' index to range array
    Dim nRng        As Long     ' number of ranges

IMO, an appropriate usage for a type declaration is for literal constants:

    Dim d As Double
    Dim i As Long
 
    d = 1#
    i = 1&

 

[kpark91]

Ahhh ok.
Thank you very much for the kind explanation