Hello,

In order to test my perl scripts, I want to override global variables (defined with the our keyword in a separated module).

Basically I have a working solution, but I don't really know if there's a better way to do that. And I need some clarifications.

To explain my issue, I reduced the code to 3 files :

- consts.pm which declare globals variables and set their content.

- logging.pm which will use consts.pm and use the global vars

- run-unit-tests.pl which overrides the content of these variables

My current solution is like this :

consts.pm 
use Exporter;

our @ISA = 'Exporter';
our @EXPORT = qw($VAR1 $VAR2);

our $VAR1="var1";
our $VAR2="var2";


1;

[download]
logging.pm 

use consts;
our ($VAR1, $VAR2);

print "Import...\n"; 
print "VAR1 : [$VAR1]\n";
print "VAR2 : [$VAR2]\n";

sub logging_func() {
        print "Running function...\n";
        print "VAR1 : [$VAR1]\n";
        print "VAR2 : [$VAR2]\n";
}
         
1;

[download]
run-unit-tests.pl 
use consts;

our ($VAR1, $VAR2);

local $VAR1 = "override1";
local $VAR2 = "override2";

use logging;

logging_func();

[download]

The produced output is like this : 

Import...
VAR1 : [var1]
VAR2 : [var2]
Running function...
VAR1 : [override1]
VAR2 : [override2]

[download]

Note that I use "local" because seems like this is the good option to override global vars (I'm reading the camel book). Seems like the override only works when I call the function. That's weird because I modified the value before including the logging module.

Other topic, could you please tell me when and why I should use (or not use) the Exporter core module. Because removing it seems to have no impact at all...

Next 3 code snippets produce the same output without teh use of Exporter code module.

consts.pm 
our $VAR1="var1";
our $VAR2="var2";

1;

[download]
logging.pm 
use consts;
our ($VAR1, $VAR2);

print "Import...\n"; 
print "VAR1 : [$VAR1]\n";
print "VAR2 : [$VAR2]\n";

sub logging_func() {
        print "Running function...\n";
        print "VAR1 : [$VAR1]\n";
        print "VAR2 : [$VAR2]\n";
}
         
1;

[download]
use consts;

our ($VAR1, $VAR2);

#print "VAR1 : [$VAR1]\n";
#print "VAR2 : [$VAR2]\n";

local $VAR1 = "override1";
local $VAR2 = "override2";

use logging;

logging_func();

[download]

When I run perl run-unit-tests.pl I get this output: 

Import...
VAR1 : [var1]
VAR2 : [var2]
Running function...
VAR1 : [override1]
VAR2 : [override2]

[download]

I thought that using a package name was a possible solution but it isn't... As you can see on the next code snippets :

consts.pm 
use Exporter;

package consts;

our $VAR1="var1";
our $VAR2="var2";


1;

[download]
logging.pm 
use consts;

print "Import...\n"; 
print "VAR1 : [$consts::VAR1]\n";
print "VAR2 : [$consts::VAR2]\n";

sub logging_func() {
        print "Running function...\n";
        print "VAR1 : [$consts::VAR1]\n";
        print "VAR2 : [$consts::VAR2]\n";
}
         
1;

[download]
run-unit-tests.pl 
use consts;

$consts::VAR1 = "override1";
$consts::VAR2 = "override2";
# OR
#local $consts::VAR1 = "override1";
#local $consts::VAR2 = "override2";

use logging;

logging_func();

[download]

This produce the same output : 

Import...
VAR1 : [var1]
VAR2 : [var2]
Running function...
VAR1 : [override1]
VAR2 : [override2]

[download]

Note that using "local" keyword during overriding step does not change anything.

If I use $main without specifying the package name, I have the exact same behavior (not a surprise of course).

So to summarize :

- Is it a better solution than mines ?

- Could you please explain this behavior ?

- Should I see any difference if I use require instead of use?

- Why do I have no impact when I stop using Exporter module ? I can't remember why I needed Exporter (maybe because I have "use strict" and "use warnings" in the original scripts...)

I don't really want to use non core modules (I read about PadWalker somewhere). At the moment, I don't really want to use packages if possible (nothing against it, but if there's a solution with packages, there's probably another one without packages).

Thank you a lot by advance.

And... I'm pretty new to perl, and I would say... perl rocks!

Regards.

Thibault

In reply to Seeking the right way to override global variables by contra-sh

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