Good coding practices in AutoIt

[czardas]

I was thinking about the whole "avoid using Global variables" recently and decided to check something.

I have a fairly large script (large for me) that I've been writing/playing around with that includes a few UDFs from here and some standard UDFs as well. Right now my script currently has 30 or so variables declared as Global, not including variables assigned to GUI controls, which I should probably put into an array at some point. What is the general prohibition against using Global variables? When you're sure there won't be any changes to them that you're not 100% aware of, so you are sure that the values they hold will be the expected values? Is it just some type of argumentum ad populum or is there something more concrete than just a lot of people saying "don't do this"? Because if it's the former, then can anyone explain where this mindset comes from, and if it's the latter can anyone explain why it's a "bad thing"?

Have you read the following?

Variables should always be declared in the smallest scope possible in any language (for languages that support it). For example, don't front-load your functions with all the variable declarations. Declare variables right before they are used. If a variable doesn't need to exist in global scope then use it in local scope. Prefer function return values and function parameters to pass data around rather than global variables. Keep variables in existence no more than necessary.

Why do you think Valik said this? Anyone have any idea?

Edited February 16, 2013 by czardas

[Xandy]

Valik said that because, it is the optimal memory usage for a program?

Simpler to read, better design.

Not the easiest to correctly conceive?

I'm not entirely sure, but I think that is the idea.

[BrewManNH]

My whole point was that so far no one has explained why global variables are supposedly bad, they've just said don't use them. Then I get pointed to where someone else says the same thing, but again not why. Which is why asked whether everyone says the same thing because everyone else says the same thing?

[Xandy]

I use globals, else I may not bother to finish the program.

I don't think globals are bad at all, and my local friends who argue that global is horrible programming practice, don't program anything.

So their opinion is not valid to me.

I am very clear that I can run into trouble with globals, but they can also save me time.

EDIT:

Namespace is the first problem using globals that comes to mind.

I try to use local of course.

Edited February 16, 2013 by Xandy

[BrewManNH]

The script that I mentioned is using so many globals because it's using OnEvent mode rather than the message loop mode. Which means a lot of variables are assigned to things, that if I was able to pass them as parameters, it would mean less globals of course. But some of them can't be passed that way, so I had to make them global.

[czardas]

I don't believe Valik would just simply regurgitate information without scrutiny. The less resources you have floating around, the less chance of something breaking. In the case in question, global variables are more likely to cause conflicts and this may take more time to fix if the variables are accessed frequently throughout the script. So we have several objections to using globals when not needed. I think the first statement says it all though: 'variables should always be declared in the smallest scope possible'.

Edited February 16, 2013 by czardas

[BrewManNH]

So we have several objections to using globals when not needed. I think the first statement says it all though: 'variables should always be declared in the smallest scope possible'.

I would agree with that, don't use them when not needed, but don't not use them just because some said "globals are bad". Also, using the Local declaration in a Global scope is gilding the lily and serves no purpose from the way AutoIt actually sees them.

[czardas]

@BrewmanNH - I agree. Sometimes you have no choice other than to use globals, although more often than not - globals are not really needed.

Declaring globals as local to the global scope is valid if you later intend to insert the code into a function. Otherwise, although it's not strictly incorrect to decale them as local, there's no need to explicitly declare them at all; for the reason you just mentioned. When you know what scope the variable needs to be, then I would say it's best practice to explicitly declare it in the most appropriate scope from the point of view of readability. If that happens to be global, then use the keyword Global rather than using local declaration.

Edited February 17, 2013 by czardas

[guinness]

I would agree with that, don't use them when not needed, but don't not use them just because some said "globals are bad". Also, using the Local declaration in a Global scope is gilding the lily and serves no purpose from the way AutoIt actually sees them.

No, but then if the variable is only used in the scope it's declared in then it's Local. Just a shame AutoIt treats it as Global.

As Valik has said before, sometimes AutoIt forces you to use Global, as is the case with OnEvent mode. You just have to play smart and know how manage them correctly. Hint: I posted a link about it a couple of posts back.

[czardas]

No, but then if the variable is only used in the scope it's declared in then it's Local. Just a shame AutoIt treats it as Global.

How else would you have it be treated? That's the only option available, right?

Edited February 16, 2013 by czardas

[guinness]

Like this...

Local $sString = ''
$sString = 'Some variable.' ; This variable wouldn't be seen in any other function.

Func Example() ; Random function.
    Local $vVar = ''
    $vVar = 'Blah'
EndFunc   ;==>Example

Func SomeFunc()
    $sString = 'Test' ; This is not the variable above, but a Local variable that isn't explicitly declared with the Local keyword.
EndFunc   ;==>SomeFunc

$sString ='Blah' ; This would be the variable declared at the start of the script as it's in the same scope.

[BrewManNH]

Calling a grape a football doesn't make it a football. There's only 2 scopes in AutoIt, and using "Local" in a global scope doesn't make it Local to any scope, so using Local is the wrong way to demonstrate to users how to write good code. I said it before, and I will say it again, if you're using it in a Global scope, use the Global keyword.

If you're going to use it that way, might as well dispense with the Global keyword completely because it's just redundant.

[guinness]

The code above is the same as this...

WrappedAround()

Func WrappedAround()
    Local $sString = ''
    $sString = 'Some variable.' ; This variable wouldn't be seen in any other function.
    $sString = 'Blah' ; This would be the variable declared at the start of the script as it's in the same scope.
EndFunc   ;==>WrappedAround

Func Example() ; Random function.
    Local $vVar = ''
    $vVar = 'Blah'
EndFunc   ;==>Example

Func SomeFunc()
    $sString = 'Test' ; This is not the variable above, but a Local variable that isn't explicitly declared with the Local keyword.
EndFunc   ;==>SomeFunc

Is the variable Global? No, it's Local, I just didn't wrap it in a function. Global isn't redundant as this would be Global...

GLobal $g_sString = '' ; This variable is used in two functions, thus it's Global.
Local $sLocalVar = ''

Func Example() ; Random function.
    Local $vVar = ''
    $vVar = 'Blah'
    $g_sString  'Global var changed'
EndFunc   ;==>Example

Func SomeFunc()
    $g_sString  'Global var changed again'
    $sString = 'Test' ; This is not the variable above, but a Local variable that isn't explicitly declared with the Local keyword.
EndFunc   ;==>SomeFunc

$sLocalVar = 'Changed.' ; This variable isn't used in any other function.

If you can prove I'm wrong, then I would be happy to change my thought process.

Edited September 4, 2015 by guinness

[czardas]

Like this...

Local $sString = ''
$sString = 'Some variable.' ; This variable wouldn't be seen in any other function.

Func Example() ; Random function.
    Local $vVar = ''
    $vVar = 'Blah'
EndFunc ;==>Example

Func SomeFunc()
    $sString = 'Test' ; This is not the variable above, but a Local variable that isn't explicitly declared with the Local keyword.
EndFunc ;==>SomeFunc

$sString ='Blah' ; This would be the variable declared at the start of the script as it's in the same scope.

I don't get the problem here. Your string variable exists in the global scope, You modify it using a function. The pre-existing variable is not reclared in the function. How else could it work? Edited February 17, 2013 by czardas

[guinness]

Calling a grape a football doesn't make it a football. There's only 2 scopes in AutoIt, and using "Local" in a global scope doesn't make it Local to any scope, so using Local is the wrong way to demonstrate to users how to write good code. I said it before, and I will say it again, if you're using it in a Global scope, use the Global keyword.

If you're going to use it that way, might as well dispense with the Global keyword completely because it's just redundant.

Also Valik has pointed this out to you before in the help file thread.

[czardas]

It is clear that you can declare a Global variable in different ways in AutoIt. That is not in dispute here.

[guinness]

Please forget the names I'm using for the variables. That variable $sString is never used in a function and thus is Local to the scope it was declared in.

Local $sString = ''
$sString = 'Some variable.' ; This variable wouldn't be seen in any other function.

Func Example() ; Random function.
    Local $vVar = ''
    $vVar = 'Blah'
EndFunc   ;==>Example

Func SomeFunc()
    Local $sStringEx = 'Test' ; This is not the variable above, but a Local variable that isn't explicitly declared with the Local keyword.
EndFunc   ;==>SomeFunc

$sString = 'Blah' ; This would be the variable declared at the start of the script as it's in the same scope.

Please read >>

[czardas]

All variables are local. Global variables are a subset. It is not bad practice to declare variables as Global. Correcting mitakes that don't exist serves no purpose.

Edited February 17, 2013 by czardas

[guinness]

Well in normal circumstances I would agree, but this thread is about pointing out mistakes and providing users with the right approach to coding.

Edited February 17, 2013 by guinness

[BrewManNH]

Please forget the names I'm using for the variables. That variable $sString is never used in a function and thus is Local to the scope it was declared in.

Please read >>

But, in AutoIt, and most other languages, it's a global variable. and using the Local keyword confuses that.