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  1. #1
    Moderator VBAX Master georgiboy's Avatar
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    Question To declare or not to declare

    Hi everyone,

    I intend this thread to be a general discussion on the topic of variable declaration.

    Iím interested in hearing your personal opinions on whether or not to declare variables. Please share your experiences and provide arguments for and against variable declaration, along with examples if possible.

    Iím not looking for a definitive answer on whether we should declare variables, as I understand this is largely a matter of personal style. Instead, I hope this discussion will offer insights that help others decide whether variable declaration aligns with their coding style.

    Personally, I believe in declaring variables, and here are a few reasons why. I may post some examples later in the thread:

    • Memory Management: By specifying the data type, VBA allocates the right amount of memory for the variable.
    • Code Readability: Well named variables make your code easier to understand.
    • Error Checking: Declaring variables helps catch errors where a variable might be used incorrectly.
    • Optimization: The VBA compiler can optimize the code better if it knows the data types in advance.

    REMEMBER, this is a discussion and not an argument so play nice.

    Have a nice day...

    George
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  2. #2
    VBAX Master Aflatoon's Avatar
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    Devil's advocate:
    Memory management: is irrelevant in pretty much all code that I've seen in forums.
    Code readability: doesn't actually require you to declare your variables. Also, variable naming and where to declare is a whole other flame war.
    Error checking: can also give a false sense of security as the compiler isn't necessarily 100% reliable on that front
    Optimisation: see memory management

    Against declaring:
    Saves typing and therefore reduces the risk of RSI and/or arthritis in later life

    I'm not sure I've ever seen any other arguments against it.
    Be as you wish to seem

  3. #3
    Moderator VBAX Wizard Aussiebear's Avatar
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    I am a firm believer in declaring your variables. Keeps your code tidy and readable, more so if the code become the responsibility of someone else to maintain it. For those prolific writers of code, it enables you to remember what your code is representing months down the track.
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  4. #4
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    I declare my variables for the purpose of error checking (primarily). I had my misses in the past and cost me dearly.

  5. #5
    VBAX Sage
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    My $0.02 ---

    If a variable is not declared, then it's a Variant, which means anything can be assigned or assigned again

    I prefer to get a runtime or development time error since I want all the help I can get

    'Option Explicit
    
    Sub NotDelcared()
        x = 1234
        x = "asdfg"
        x = True
        Set x = Worksheets(1)
        MsgBox x.Name
    End Sub
    
    
    Sub Delcared()
        Dim n As Long
        Dim s As String
        Dim b As Boolean
        Dim o As Worksheet
        n = 1234
        s = "asdfg"
        b = True
        Set o = Worksheets(1)
        MsgBox o.Name
        n = s
    End Sub
    Capture.JPG
    Last edited by Paul_Hossler; 05-17-2024 at 08:07 AM.
    ---------------------------------------------------------------------------------------------------------------------

    Paul


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  6. #6
    Moderator VBAX Master georgiboy's Avatar
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    I have to agree on that part @Paul_Hossler,

    In my experience, I am able to capture errors earlier in the code and (to me) they make more sense as to where the errors form. Take the below for example, without declarations the error forms on the last line and (again, to me) does not seem completely obvious as to why:
    Sub NotDeclared()    
        s = "Hello world"
        
        ' some code...
        
        n = s
        
        ' Lots and
        ' lots and
        ' lots of code
        
        MsgBox n + 1 '<<< Error comes here
    End Sub
    Whereas with the variables being declared (below), the error comes much earlier in the code and seems (to me) more obvious as to what the problem is as it comes when passing a value to a variable. Worth noting also that the error was triggered before the 'Lots of code' part, so if you are into writing long sub routines then it could save you some scrolling up and down:
    Sub Declared()
        Dim s As String, n As Long
        
        s = "Hello world"
        
        ' some code...
        
        n = s  '<<< Error comes here
        
        ' Lots and
        ' lots and
        ' lots of code
        
        MsgBox n + 1
    End Sub
    I would still like to see some arguments for not declaring as I am sure there are some logical arguments and thought processes behind both methods.
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  7. #7
    Distinguished Lord of VBAX VBAX Grand Master Bob Phillips's Avatar
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    I am very pro declaring variables, and adding Option Explicit to all modules.

    Rory's arguments, Devil's advocate I know, but for, even if the compiler is not 100% accurate, surely it is better to get whatever comfort it does provide. And you can also get extra comfort when using the variable, I declare the name with a form of camel-case, but type them in lower-case. If I type it correctly, it upshifts, if I don't I get an immediate feedback that I have erred. Against, the extra typing is totally irrelevant in my eyes, we don't write enough code to make declaring variables onerous. You can save later when you use a variable by typing a few letters, then use Ctl-spacebar to auto-complete.

    Bill Jelen doesn't believe Option Explicit, he and I have had this discussion so often. but I haven't convinced him.
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  8. #8
    VBAX Master Aflatoon's Avatar
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    For the record, I always declare. Even as lazy as I am, I can’t see any benefit to not doing so; and there are definite benefits to doing it, as everyone has mentioned.

    still waiting for a certain someone to show up in this thread…
    Be as you wish to seem

  9. #9
    Moderator VBAX Wizard Aussiebear's Avatar
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    I doubt if he will....
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  10. #10
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    Surely you all have 'Require variable declaration' ticked to force it!


    Dim ImportantValue as string
    ImportantValue="Important"
    
    
    If ImpotantValue="" then
        Msgbox "Why have I spent hours debugging this code to find out why this message keeps appearing?"
    end if
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  11. #11
    Moderator VBAX Wizard Aussiebear's Avatar
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    Quote Originally Posted by mark007 View Post
    Surely you all have 'Require variable declaration' ticked to force it!
    True, but you need to want to do this.
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  12. #12
    Declaring actually SAVES typing. Especially if a variable is used more than once or twice: type one or two characters, hit control+Space and bam! And declaring vairables using the correct type allows intellisense to work.
    Regards,

    Jan Karel Pieterse
    Excel MVP jkp-ads.com

  13. #13
    Moderator VBAX Master georgiboy's Avatar
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    Quote Originally Posted by Jan Karel Pieterse View Post
    declaring vairables using the correct type allows intellisense to work.
    This is a good point, saves even more typing.

  14. #14
    VBAX Master Aflatoon's Avatar
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    Quote Originally Posted by Jan Karel Pieterse View Post
    Declaring actually SAVES typing. Especially if a variable is used more than once or twice: type one or two characters, hit control+Space and bam!
    Not if you also only ever use 1-3 characters for your variable names...
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  15. #15
    Distinguished Lord of VBAX VBAX Grand Master Bob Phillips's Avatar
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    Quote Originally Posted by Aflatoon View Post
    Not if you also only ever use 1-3 characters for your variable names...
    Many moons ago, in my days as a Cobol programmer, a colleague would declare their variables as a,b,c,d, etc. Drove me mad.
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  16. #16
    Moderator VBAX Wizard Aussiebear's Avatar
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    Quote Originally Posted by Bob Phillips View Post
    Many moons ago, in my days as a Cobol programmer, a colleague would declare their variables as a,b,c,d, etc. Drove me mad.
    oooookay...... !!!!

    On second thoughts, you are not mad, just English.
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  17. #17
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    Quote Originally Posted by Bob Phillips View Post
    Many moons ago, in my days as a Cobol programmer, a colleague would declare their variables as a,b,c,d, etc. Drove me mad.
    How about aa, a1, a_1, _a, _a1, ...
    ---------------------------------------------------------------------------------------------------------------------

    Paul


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  18. #18
    Moderator VBAX Wizard Aussiebear's Avatar
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    Right so at this stage, its 99.9% in favour of declaring and 0.1% as not declaring. Mind you the 0.1% is for the guy who thinks its not necessary but couldn't find the courage to post.
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  19. #19
    Moderator VBAX Wizard Aussiebear's Avatar
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    Hmmm.... you are more English than I thought.
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