Question on global scope of variables within function and/or program

[poila]

I was recently trying to fix a bug in a program I was handed over for about 3 weeks, but has left me stuck for a long while, and asking others in my office is not a viable option. I did a code review on my own and had doubts. So I came here to ask.

What is the default scope of variables when declared within a function, if "Global" and "Local" are not used?

Sample code:

Func showSidebar($guiEvent, $refresh = False)
    If ($refresh) Then
    $previousFormName = Null;
    EndIf
    
    ; Do stuff...

    If $guiEvent <> Null Then
    If $guiEvent[0] == $sideButton_Y Then
        $previousFormName = Null
        $helpStatus = True
    ElseIf $guiEvent[0] == $sideButton_N Then
        $previousFormName = Null
        $helpStatus = False
    EndIf
    EndIf

    ; Do stuff again...
    ; Declaration of variables - does scope change?
    Global $currentForm, $previousFormName, $currentFormName

$currentFormName = ""

$currentForm = WinGetHandle("")

; Do more stuff... If $currentFormName <> $previousFormName Then ; Clear buttons EndIf ; Do even more stuff... $previousFormName = $currentFormName EndFunc

This function would be called within a "While 1" loop when loading a GUI:

While 1
    $guiEvent = GUIGetMsg(1)
    showSidebar($guiEvent)
    Switch $guiEvent[0]
        Case $guiEvent[0] = $blahButton
            ; Do stuff...
    EndSwitch
WEnd

Thing is, when the application runs initially, the variables $currentForm, $previousFormName, and $currentFormName are marked as initially undeclared. But once the function runs, all of them are within Global scope of the application.

If I changed the code such that $currentForm, $previousFormName, and $currentFormName are declared as Global at the beginning of the code, the function would not behave as intended.

As for resetting variables declared Global within the function, is the following code considered okay for resetting variables?

$currentForm = ""
$previousFormName = ""
$currentFormName = ""

[Melba23]

poila,

 

What is the default scope of variables when declared within a function, if "Global" and "Local" are not used?

By default, AutoIt treats all variables declared outside functions as Global - even if they are declared as Local. All variables declared inside functions are Local, unless specifically declared as Global (which is regarded as poor practice).

You need not respecify the scope when resetting simple variables as they retain their initial scope. But you do need to specify the scope when resetting arrays or you will get a syntax error as array declarations require a scope at all times.

The Variables - using Global, Local and ByRef tutorial in the Wiki should be your next port of call.

M23

Edited May 13, 2014 by Melba23
Typo

[poila]

poila,

 

By default, AutoIt treats all variables declared outside functions as Global - even if they are declared as Local. All variables declared inside functions are Local, unless specifically declared as Global (which is regarded as poor practice).

You need not respecify the scope when resetting simple variables as they retain their initial scope. But you do need to specify the scope when resetting arrays or you will get a syntax error as array declarations require a scope at all times.

The Variables - using Global, Local and ByRef tutorial in the Wiki should be your next port of call.

M23

That was mildly helpful. I did remember reading that tutorial awhile ago, had abit of trouble with applying scope concepts onto legacy code. I went to play around with my variables' scope just now.

Now I tried rewriting the function like this:

Func showSidebar($guiEvent, $refresh = False)
    Local Static $currentForm, $previousFormName, $currentFormName
    If ($refresh) Then
        If IsDeclared($previousFormName) Then
             $previousFormName = Null;
        EndIf
    EndIf
    
    ; Do stuff...

    If $guiEvent <> Null Then
    If $guiEvent[0] == $sideButton_Y Then
        If IsDeclared($previousFormName) Then
             $previousFormName = Null;
        EndIf
        $helpStatus = True
    ElseIf $guiEvent[0] == $sideButton_N Then
        If IsDeclared($previousFormName) Then
             $previousFormName = Null;
        EndIf
        $helpStatus = False
    EndIf
    EndIf

    ; Do stuff again...
    $currentFormName = Null
    $previousFormName = Null
    $currentForm = WinGetHandle("")

    ; Do more stuff... 
    If $currentFormName <> $previousFormName Then 
        ; Clear buttons 
    EndIf 
    ; Do even more stuff... 
    $previousFormName = $currentFormName 
EndFunc

Unfortunately, the thing is that another function needs to make use of the variable $currentFormName, which previously was in Global scope but because I tried and experimented with Local Static, obviously it seemed to be effective within function showSidebar().

IsDeclared() would cause the script to prevent compiling because it detected $previousFormName as undeclared, though after checking with previous programmer, he mentioned that the way the earlier code shown was written was intentional (hack-ish, I feel).

Also, as I have shown in my earlier post, because showSidebar() is within a While 1 loop, this is called continually until the While loop is exited, meaning that the variable $previousFormName would be continually reset only if I were to use the newer way I wrote.

(The older code I showed meant that though showSidebar() is called continually, $previousFormName is only modified once, so that the sidebar GUI won't reset infinitely.)

$currentForm is used for grabbing GUI handles.

Need to show additional code for possible troubleshooting - this occurred before resetting variables and after $previousFormName = $currentFormName:

expandcollapse popup

$pos = WinGetPos($currentForm)

    If $currentFormName <> "" Then
        If $currentFormName <> $previousFormName Then
            If $sideButton_Y <> Null Then
                GUICtrlSetState($sideButton_Y, $GUI_HIDE)
            EndIf
            If $sideButton_N <> Null Then
                GUICtrlSetState($sideButton_N, $GUI_HIDE)
            EndIf

            GUISwitch($currentForm)
            ; Show help button on main forms
            If $currentFormName == "myCurrentForm" Then
                If $helpStatus Then
                    $sideButton_N = GUICtrlCreateLabel("?", $pos[2] - 44, 2, 20, 20)
                    GUICtrlSetBkColor(-1, $GUI_BKCOLOR_TRANSPARENT)
                    GUICtrlSetFont(-1, 14, 1000, 0, "Tahoma")
                    GUICtrlSetColor(-1, 0xeeeeee)
                Else
                    $sideButton_Y = GUICtrlCreateLabel("?", $pos[2] - 44, 2, 20, 20)
                    GUICtrlSetBkColor(-1, $GUI_BKCOLOR_TRANSPARENT)
                    GUICtrlSetFont(-1, 14, 1000, 0, "Tahoma")
                    GUICtrlSetColor(-1, 0xeeeeee)
                EndIf
            EndIf
        EndIf
    EndIf


    If $helpStatus Then
        If $currentFormName <> "" Then
            WinMove($sidebarForm, "", $pos[0] + $pos[2], $pos[1], $const_HelpWidth, $pos[3])

            If $currentFormName <> $previousFormName Then
                calledAnotherFunction()

                ; $currentArrayIndex is some Global array variable, don't think too much about it
                If $currentArrayIndex >= 0 Then
                    ; Do something
                Else
                    showInput("Done!")
                EndIf

                If $currentFormName == "myCurrentForm" Then
                    ; Do something else
                EndIf

                GUISetState(@SW_SHOWNOACTIVATE, $sidebarForm)
            EndIf
        Else
            calledAnotherFunction()
        EndIf
    Else
        calledAnotherFunction()
    EndIf

calledAnotherFunction is as follows:

Func calledAnotherFunction()
    ; Hide stuff
    GUISetState(@SW_HIDE, $sidebarForm)
EndFunc

[Melba23]

poila,

 

That was mildly helpful

And I find your reply mildly insulting.

 

Unfortunately, the thing is that another function needs to make use of the variable $currentFormName

Then it needs to be Global in scope or passed to the other function as a parameter.

M23

[jdelaney]

If you don't define the variable in a function as local, and there is already a global match (not case sensitive), the global will be overwritten.

Gotta be careful of that...

$i = 10
Function()
ConsoleWrite($i & @CRLF)
Func Function()
    $i = 30
EndFunc

^output is 30, not 10.

$i = 10
Function()
ConsoleWrite($i & @CRLF)
Func Function()
    Local $i = 30
EndFunc

^output is 10

Edited May 13, 2014 by jdelaney

[poila]

I pushed the variables $currentForm, $previousFormName, $currentFormName to the top of source code, declared as Global, outside the function.

Additionally, I did not re-declare the variables in the function to Local.

Earlier code of function "showSidebar", I refactored first part to this:

If $previousFormName <> Null Then
    $previousFormName = Null
EndIf
$currentForm = Null
$currentFormName = Null

; Get currently focused form
$currentForm = WinGetHandle("")

Sidebar GUI keeps flashing instead.

Reason for this refactor was to overcome another issue I need to raise, which is randomly-missing/hiding GUI controls.

Welp?

Edited May 13, 2014 by poila

[guinness]

Too late to the party I see. Word of advice to poila, with global variables use a prefix of $g_ e.g. $g_sMyName, as it's easy to distinguish what is local and global.

(not case sensitive)

I really love case-sensitive languages e.g. C#. (100% serious comment)

[poila]

Hi guinness,

I have already renamed my variables according to the standards used in the Best Practices tutorial in the AutoIt Wiki.

eg.) The handle $currentForm is now $g_hCurrentForm (global, handle).

I dug deeper into the problem, and it turned out that the functions/variables that I mentioned in this thread so far aren't the cause of the problem.

It turned out that 2 other global variables - declared uninitialized at the top of source code - were being used and modified within the function "showSidebar()"

If $currentFormName <> "" Then
    ; If focused form on current iteration is different from previous iteration then initiate help sequence
    If $currentFormName <> $previousFormName Then
        ; Remove previous buttons
        If $sideButton_Y <> Null Then
            GUICtrlSetState($sideButton_Y, $GUI_HIDE)
        EndIf
        If $sideButton_N <> Null Then
            GUICtrlSetState($sideButton_N, $GUI_HIDE)
        EndIf
        EndIf
EndIf

I am thinking of extracting out the contents of whatever GUI controls and handles (like showing the contents of an array) somewhat similar in fashion to the WinListChildren() UDF shown in this link: '?do=embed' frameborder='0' data-embedContent>>

Is there a similar function (native or UDF) used for displaying GUI handles into an array/list?

Thanks in advance.

EDIT: It turned out that the 2 global variables I mentioned in this particular reply are the culprit to my predicament. It was more of a fundamental code design flaw rather than the way the functions I shared here were used/written. Thanks again everyone. At the meantime, I might leave the question on how to display member GUI handles into an arraylist as an open question, but probably in another thread.

Edited May 14, 2014 by poila