Using a variable in a function 1

[Frink]

Hallo,

Why can't a function change a variable defined in the calling script?
[tt]
$scriptvar=2
function scopetest
{
"scopetest before $scriptvar"
$scriptvar=$scriptvar+1
"scopetest after $scriptvar"
}
"Before $scriptvar"
scopetest
"After $scriptvar"
[/tt]
Gives:
[tt]
Before 2
scopetest before 2
scopetest after 3
After 2
[/tt]
The results show that a copy of the variable was updated within the function, not the actual variable.
I would have expected
[tt]
Actual 3
[/tt]

Any ideas/explanation,

-Frink

 

[Geates]

The $scriptvar within the functions scope is private; it is unaware of the $scriptvar outside. Either the variable needs to be defined in the global scope

$[b]Global:[/b]scriptvar = 2

or the variable needs to be passed to the function and then return (this option is desirable)

function scopetest([b][int] $var[/b])
{
   $var = $var + 1
   [b]return $var[/b]
}

$scriptvar = 2
scopetest($scriptvar)

# Output is 3

-Geates

 

[Frink]

Cheers Geates,

Have you tried it with $global:scriptvar=2?
I did and it produced the same results.

Your second method isn't suitable for my purposes as I will have lots of script-level variables.

- Frink

 

[crobin1]

If you're going to access variables that are outside the scope of the function, you have to include the scope qualifier even within the function. Unlike with some languages, declaring a variable to be "Global" doesn't automatically mean assignments to that variable will access the Global scope.

Try this:

$Global:scriptvar = 2
function scopetest
{
    "scopetest before $scriptvar"
    $Global:scriptvar=$Global:scriptvar+1
    "scoptetest after $scriptvar"
}
"Before $scriptvar"
scopetest
"After $scriptvar"

Note that to be really explicit you can also use $Global:scriptvar in your output strings:
"Before $Global:scriptvar"

In PowerShell type "help about_scope" for more info

 

[Geates]

Frink -
>Your second method isn't suitable for my purposes as I will have lots of script-level variables.<

Be careful when using global scope variables. Your code may - unitentionally - fail epically.

However, you do have a bit of a safety net. As crobin1 stated, "you have to include the scope qualifier".

-Geates

 

[Frink]

Cheers. Is it just me, or is this pants?

- Frink