Initializing variables

Is it necessary to initialize variables or is it OK to let the compiler do it?  I know in languages like C++ it's absolutely necessary to initialize variables, but I'm not sure about VB6.

Please explain answer.

Thanks.
halfondjAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

sirbountyCommented:
If you don't declare a variable, it's declared as variant which takes up more resources.
http://juicystudio.com/tutorial/vb/variables.asp gives a great explanation.
0
Jaime OlivaresSoftware ArchitectCommented:
Also, even languages like VB6 or ASP or PHP allow you not to declare variables, it is a good practice because it contributes to readability:

Dim var1 as string     ' Explain here purpose of this variable
Dim var2 as integer   ' Explain here purpose of this variable
Dim var3 as double    ' Explain here purpose of this variable
0
Erick37Commented:
When you Dim a variable, VB is kind enough to initialize it for you.

Numbers are set to 0
Strings are empty
Objects are Nothing

If you have Form level variables or even Static variables inside form procedures, they can retain values even after you unload the Form.  If you need to have them reset, either do it via code in Form_Load, or be sure you Set FormX = Nothing before you reload it.  That will force the form completely out of memory, and the variables will reinitialize when the form loads again.

Hope it helps!
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Ultimate Tool Kit for Technology Solution Provider

Broken down into practical pointers and step-by-step instructions, the IT Service Excellence Tool Kit delivers expert advice for technology solution providers. Get your free copy now.

Erick37Commented:
An Example

Private sTest as String  'Form level variable initializes to "" on Form_Load

Sub Command1_Click()

    Dim i as Long   ' Dimmed variable is reste to 0 each time this Sub is entered
    Static lx as Long ' Static variables initialize to 0, but retain values.

    Debug.Print i, lx

    lx = lx + 1

End Sub
0
fulscherCommented:
Two comments in addition to those of sirbounty:

Example:
    Dim ikl as Long
    ikI = test(a, b)   'note: Uppercase i instead of lowercase L
    Debug.Print ikl    'always prints 0

This kind of bugs is rather difficult to find. Declaring variables helps you to avoid this; if you had Option Explicit turned on, the compiler would have complained about your using an undeclared variable "ikI".

Also, by declaring them to have a specific data type, you can avoid certain types of errors where you pass the wrong datatype to a function, for example. This is a problem if a function can handle one option but not the other:

    Dim v as Variant
    if Day(Now) = 1 then
        v = "seven"
    else
        v = 7
    end if

    Debug.Print v / 7   ' Crashes ONLY on the first day of a month. Nasty.

If you had declared v as numeric type, this error would have been be possible.

So, by declaring variables, you remove amiguity from your code - which is always a good thing to do...

0
fulscherCommented:
Ups - sorry: Just re-read the question.

"Is it necessary to initialize variables"

You CAN in C/C++, although it's not necessary, but good style. Helps avoiding strange errors.
You CANNOT in VB6, unfortunately, if I'm not mistaken. Initialising a variable is especially useful if it's a static variable.

Compare these two bits of code:

Sub DoIt1
   Static myStr as String ' must contain "hello" in the first call
   
   if myStr = "" Then
       myStr = "hello"
   end if

   Debug.Print myStr
   myStr = myStr & "!"
End Sub

Sub DoIt2
   Static myStr = "hello"
   Debug.Print myStr
   myStr = myStr & "!"
End Sub

So, initializing variables certainly has its advantages, but is not strictly necessary.

Jan
0
halfondjAuthor Commented:
Thanks for all the replies.  I knew about declaring variables and I also knew it's good practice to initialize them, but I wanted to hear from the experts re:the initialization.

0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Visual Basic Classic

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.