Good coding practices in AutoIt

[BrewManNH]

I think several of the potential issues caused by the use of global variables, listed by jaberwocky6669 in are relevant to AutoIt. I also think this needs further elaboration. This is how I see it but please correct me if you know I'm wrong, or if you have information to add then please do so. These are only my thoughts on the subject - no tests have been carried out.

Potential issues affecting AutoIt:

Inadvertent changes to global data. - Higher risk (with bad coding)

That's always a risk, global or local. It depends on the skill of the person writing the script.

Re-entrant code problems with global data. - May affect multiple instances of the same running script.

Not an issue in AutoIt because variables in one instance of a running program have no effect on variables in another instance of the same program. He was talking about multi-threaded programs where another thread is writing to the same variable in the same program.

Code reuse hindered by global data. - TRUE

Very true, less global use in a function makes it easier to port it to another script later so you don't have to reinvent the wheel.

Modularity and intellectual manageability damaged by global data. - TRUE

Not sure what this means so I can't really comment on it.

Bizarre and exciting aliasing problems with global data. - Why is this a potential issue?

This isn't a problem for AutoIt because we don't have anything that would be comparable to "typedef" in AutoIt. To the best of my knowledge that is. I'm always learning some new thing is available in AutoIt that I didn't know about before.

One problem that isn't mentioned is if more than one person is working on a program and each person is writing their own piece of the puzzle, you can inadvertantly reuse a variable name that someone else used as a Global that overwrites what you THINK should be in there because your part of the pie doesn't affect it, but theirs does.

Don't get me wrong, I believe that using Global is going to give you problems if you're writing code without thinking of the whole picture when you're doing it. Passing the variables to the functions and returning the value(s) to the calling function is better than changing a Global variable in the function, but it's not always possible, and the use of a global variable makes the writing easier, but the troubleshooting a lot harder if you don't have a plan. Once again, it's going to depend a lot on the coder's skill in writing a script whether it becomes an issue.

[czardas]

Not an issue in AutoIt because variables in one instance of a running program have no effect on variables in another instance of the same program. He was talking about multi-threaded programs where another thread is writing to the same variable in the same program.

As I said, I have not tested it, but I have had issues with inadvertant information shared between two instances of the same program in the past. It appeared to boil down to duplicate global variables, [edit] although looking at it again, I now think the problem was actually caused by something else, so please don't quote me on this [/edit]. The only way I could find to solve it was to force a single instance of my program.

Not sure what this means so I can't really comment on it.

It simply states that writing complex code is hindered by using global variables. This is one of the issues you raised yourself about sharing workload. Also, if you declare a variable in the local scope, the assigned value is right in front of your eyes. That's the easier manageability part. Edited February 21, 2013 by czardas

[jaberwacky]

Here is an example from that book that I should have included. This example demonstrates the first point of inadvertent changes.

Global $the_answer = get_the_answer()

Global $other_answer = get_other_answer() ; assume that get_other_answer modifies $the_answer

Global $average_answer = ($the_answer + $other_answer) / 2 ; and now, $the_answer doesn't store the value you would expect

This would be fine for small programs. 10,000+ programs with hundreds of functions that modify global data might be a nightmare.

[czardas]

Here's another interesting topic about globals:

Be sure to read #entry766066.

Edited February 22, 2013 by czardas

[BrewManNH]

Post 9 is informative, but not relevant to AutoIt, Au3Check will not throw an error message, but the script will when you run it.

[czardas]

Post 9 is informative, but not relevant to AutoIt...

I disagree.

Firstly: I trust Valik's judgement.

The problem isn't as possible in AutoIt but it's still not hard to do for any non-trivial script.

Secondly: In relation to AutoIt; if this and the other points raised were as unimportant as you say, it's still better to stick to good coding practice. In my opinion, this would mean avoiding global variables wherever you can. The evidence I have read is stacked in favour of this being the better approach.

Edited February 22, 2013 by czardas

[guinness]

Another reason why explicitly declaring variables is always a good idea.

#include <MsgBoxConstants.au3>

; True will NEVER equal False.
If True = False Then $sVar = 'Test' ; This won't create an Au3Check error.
MsgBox($MB_SYSTEMMODAL, '', $sVar)

Edited September 4, 2015 by guinness

[czardas]

Another reason why explicitly declaring variables is always a good idea.

#include <Constants.au3>

; True will NEVER equal False.
If True = False Then $sVar = 'Test' ; This won't create an Au3Check error.
MsgBox($MB_SYSTEMMODAL, '', $sVar)

Surely this constitutes either a bug or a weakness in AU3Check. While I agree that explicit declaration of variables is good practice, your code can be fixed witthout the need for explicit declaration...

#include <Constants.au3>

$sVar = ""
If True = False Then $sVar = 'Test' ; This won't create an Au3Check error.
MsgBox($MB_SYSTEMMODAL, '', $sVar)
Exit

... and remain broken with explicit declaration included.

#include <Constants.au3>

; True will NEVER equal False.
If True = False Then Global $sVar = 'Test' ; This won't create an Au3Check error.
MsgBox($MB_SYSTEMMODAL, '', $sVar)

I think there are also exceptions where explicit declaration is not necessary and can even be a hinderance. I believe that one of the great features of AutoIt is that you have options such as MustDeclareVars. Setting aside any potential advantages affecting speed or unrelated issues, this flexibility makes AutoIt appealing to people with no previous programming experience. The same subject also came up

When you are learning AutoIt, which describes most readers, there is not only one learning curve to overcome. It is encouraging to the learner at each stage when they reach a certain level of understanding. I feel it is therefore good that AutoIt does not always balk when you create clumsy code. I can get to grips with conditional statements without having to know anything about Global, Local, Const or Static.

[guinness]

Surely this constitutes either a bug or a weakness in AU3Check. While I agree that explicit declaration of variables is good practice, your code can be fixed witthout the need for explicit declaration...

You kind of referenced the post already, but using Au3Check with advanced parameters will show an error.

#AutoIt3Wrapper_Au3Check_Parameters=-d -w 1 -w 2 -w 3 -w- 4 -w 5 -w 6 -w 7

...and MustDeclareVars is very limited compared to Au3Check.

[czardas]

Correct syntax and good coding practice may not necessarily be one and the same. Anyway I've moved on from there now.

[czardas]

I was just thinking about how to reduce memory use with global data and here's a method I came up with. It combines some of the ideas discussed recently in this thread.

Global $g_200_Unassigned_Elements[200] ; Declare an empty array.

For $i = 1 To 3 ; The user repeatedly calls a function.
    User_Function() ; This function requires an as yet unassigned global variable.
Next

Func User_Function()
    Have_You_Been_Here_Before() ; It is not necessary to assign values to elements until the values are needed.

    ; Do something with $g_200_Unassigned_Elements[0]
    ConsoleWrite("I only need to remember to say this if you actually visit:" & @LF)
    ConsoleWrite($g_200_Unassigned_Elements[0] & @LF)
EndFunc

Func Have_You_Been_Here_Before()
    Static $b_First_Visit = True

    If $b_First_Visit Then ; This section of code is never repeated.
        ConsoleWrite("Long time no see." & @LF)
        $g_200_Unassigned_Elements[0] = "Do you come here often?" ; Fetching this information could involve additional processing.
        $b_First_Visit = False ; memory in use
    EndIf
EndFunc

Edited February 23, 2013 by czardas

[guinness]

That's what I do these days, though for ease I use Enum to replace index values.

[acidman]

What are you guys on about really? I have no problems with Globals, I usually use global when I have a pre defined string or maybe a number, I've seen a few threads on statics but there's no use for me to use it. Global, local and Dim works fine for me in all cases, from my point of view I don't see the need for other scopes...

[guinness]

None of us have "problems" with Globals. The fact you mentioned Dim tells me you didn't read my first post.

Edit: Please only post here if you have something beneficial to add or don't quite understand a certain aspect of 'good coding practice.' Thank you.

Edited February 23, 2013 by guinness

[acidman]

No not actually, you got me there... Who reads through 200+ posts anyway?

[guinness]

Someone who cares about learning and incidentally my first post is called "Why using Dim over Local/Global is not always a good option:".

[acidman]

I only use dim for arrays, because I thought it was the best scope for arrays...

As understood from the helpfile.

Edited February 23, 2013 by acidman

[acidman]

Since we're on the topic of variables what is enum used for anyway? I'm a bit lazy to search, so perhaps you could tell me?

[guinness]

I still think you have a lot to learn acidman. Dim is a 'variable scope' keyword for when you require AutoIt to control whether or not it's in Local or Global scope depending on the variable existence, as shown in my first post. You will also see many examples that use Local/Global to declare an array, thus Dim isn't the only choice.

[guinness]

Since we're on the topic of variables what is enum used for anyway? I'm a bit lazy to search, so perhaps you could tell me?

I'm not, that's the difference. Please search the help file. Edited February 23, 2013 by guinness