Global symbols requires explicit package name

[TheDauntless]

Hey,

I keep getting this error with the following code:

#!/usr/bin/perl -w
use strict;


sub mainMenu
{
    print "Kies een optie (1-7)\n";    
    &listenForMenuChoice;
}

sub listenForMenuChoice
{
    local($choice);
    $choice = <>;
    chop $choice;
    
    use Switch;
    switch ($choice)
    {
        case "1"
        {
            $status = 1;
            &startNewOrder;
        }
        case "1"
        {
            $status = 1;
            &startNewOrder;
        }
    }
    
}

# de huidige status waar de klant in zit (komt overeen met menu opties)
global $status = undef;

Why do I keep getting this error? I'm now getting it at the first 5 lines of 'listenForMenuChoice'.


It probably has something to do with variable scope, but I've been googling for a few hours now and I can't find a descent explanation....

All help is appreciated!

 

[ishnid]

local($choice);

The 'local' function gives a temporary value to a global variable. But you're using strict and you haven't declared a global variable called $choice. That's why you're getting the error. You almost certainly want to use 'my' instead of 'local'.

 

[TheDauntless]

Ah, I get it!

So I changed those lines to:

  my $choise = <>;
    chop my $choice;

And the error is gone. Now I get another error (well, same error, different place). I'm getting it at the $status = 1; in the switch. How can I access the global variable?

Also: is "glob $status = undef;" correct? I'm just using 'glob' 'cause that turned purple in my editor (just like 'my'). (The problem is still there if I change it to 'my $status = undef')

 

[KevinADC]

drop "my" in the second line, and you almost certainly want to use chomp instead of chop::

my $choice = <>;
chomp $choice;

or all in one line:

chomp(my $choice = <>);

declare $status at the beginning of the function:

sub listenForMenuChoice
{
   chomp(my $choice = <>);
   my $status;
   use Switch;
   switch ($choice)
    {
        case "1"
        {
            $status = 1;
            &startNewOrder;
        }
        case "1"
        {
            $status = 1;
            &startNewOrder;
        }
    }
    [red]return $status;[/red]  
}

You also have to use the return() function to return a value to the caller otherwise $status will not be visible to the rest of the script.

Why do you have the same case statement twice?


------------------------------------------
- Kevin, perl coder unexceptional!

 

[TheDauntless]

I have the same case statement twice because I was in the middle of copy pasting when I posted the script .

Why do I need a return? I have declared '$status' in the main part (so not inside a routine). I just need to access THAT $status from within a routine. (Just like you would access instance variables from within a method (in an OO language))

CHOMP vs CHOP: I looked it up and I guess I better use CHOMP, but in this case it doesn't really mater (but I will change it)


I also have another question, but I'll create a new thread for that

Thank you for replying !

 

[ishnid]

chomp vs. chop: it may not matter this time but when you try to move your script from a *nix platform to a Windows one you'll be scratching your head trying to figure out why it doesn't work anymore. Best get it right first time.

 

[TheDauntless]

Ok, got that .

But I still have a question concerning the scope issue. Little example:

my $status = 0;
sub sub1
{
my $status = 1;
&sub2;
}

sub sub2
{
print my $status;
}
&sub1;

The idea is that all those $status'es should point to the same $status (the one declared in line 1). How do I do that?

 

[travs69]

stop adding my after you've declared it once if you don't want to change to scope.

my $status = 0;
sub sub1
{
	$status = 1;
	&sub2;
}

sub sub2
{
	print $status;
}
&sub1;

#or quit mixing them up and just declare new variables in each subroutine which will probably save you headaches later anyway

my $status = 0;
sub sub1{
	my $input = shift @_;
	$input = 1;
	&sub2($input);
}

sub sub2{
	my $input2 = shift @_;
	print $input2;
}
&sub1($status);

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Travis - Those who say it cannot be done are usually interrupted by someone else doing it; Give the wrong symptoms, get the wrong solutions;

 

[ishnid]

By putting 'my' before each one, you're expressly creating a new variable each time! Just create the first one using "my" and then don't qualify your use of $status thereafter and you'll be referring to the same one each time.

 

[TheDauntless]

If I don't write the 'my ' it gives the same error at that line.

my $status = undef;
sub listenForMenuChoice
{
    print "Geef uw keuze en druk op enter.\n";
    my $choice = <>;
    chop $choice;
    print "\n";
    
    use Switch;
    switch ($choice)
    {
        case "1"
        {
            $status = 1;
            &startNewOrder;
        }
}
}

It gives an error on the "$status = 1;" line.

 

[KevinADC]

what error does it give? Just saying it gives an error is useless information. The Switch module is buggy though, it often creates problems.

------------------------------------------
- Kevin, perl coder unexceptional!

 

[TheDauntless]

The same error as before; the one in the topic title

"Global symbol XXXXX requires explicit package name"

I now tried this:
$Main::counter = 1;

That seems to help. Is this supposed to be used like that?

 

[KevinADC]

A quck test seems to work OK for me:

use strict;
use warnings;
my $status = undef;
listenForMenuChoice(1);
sub listenForMenuChoice
{
    print "Geef uw keuze en druk op enter.\n";
    my $choice = shift;
    chomp $choice;
    print "\n";
    
    use Switch;
    switch ($choice)
    {
        case "1"
        {
            $status = 1;
            print $status;
        }
    }
}

------------------------------------------
- Kevin, perl coder unexceptional!

 

[ishnid]

You'd have to have declared $status using 'my' before the subroutine is declared, as opposed to just having it before your subroutine is called.

 

[TheDauntless]

Aha! That's interesting!

I'm going to try that