Call subroutine of main namespace from package in Plack

[Thenothing]

Hello everyone, I hope your are doing fine. I have this little problem, you can see the case here:

https://stackoverflow.com/questions/49770665/perl-call-subroutine-of-main-namespace-from-package

This work in console perl, but when I run with plackup I get error. Undefined subroutine &main::test

My program.pl

BEGIN {
sub test{

return "from test";

}

}

use Mypackage;

sub {
  return [ 200, [ "Content-Type" => "text/html" ], [ test() ] ];
};

Mypackage.pm

package Mypackage;

::test();

How can access to main space in plack psgi to run the function, like I do with console perl ? Thanks so much

[choroba]

Why do you need it? Calling functions from the main:: namespace in modules is a code smell. And now we also see why. How do you run the script under plackup?

Also, please, linkify the crosspost link by at least wrapping it into square brackets.

Update: I tried to just run

plackup program.pl

(and I added

1;

to the end of Mypackage.pm.

To debug, you can add

warn __PACKAGE__;

inside the BEGIN block before defining the test subroutine. You'll see that plack doesn't call your program in the main namespace.

[Thenothing]

Hi choroba, I have a main script app.psgi, inside I have several modules, modules in my local folder like module1.pm, module2.pm, etc

This modules have own functions.

In the app.psgi I have anothers functions relation to router engine urls, to dispach content according to url.

My target is set a value or get a value from main script (app.psgi) and pass that value to all modules, and retrieve the value from module via the function set in main script.

* To do this I can pass a function value to another function.
* I can create a our variable
* I can used db to retrieve data


But I want to avoid the above list, that's why the title of this thread.

[choroba]

I don't understand. A module doesn't know who calls it, it can't make any assumptions about its caller's namespace and capabilities. The contract is defined by arguments and the returned value. If you need a function called in the main program and in the modules, move it into a new module and properly use it everywhere.

[thanos1983]

Hello Thenothing,

I am not familiar with PSGI/Plack but I read your question Perl - Call subroutine of main namespace from package and I think you are looking for something like that:

main.pl

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

use Mypackage;

sub callingTest {
    my $object = new Mypackage();
    return [ 200, [ "Content-Type" => "text/html" ], [ $object->test()
+ ] ];
};

print Dumper callingTest();

__END__

$ perl main.pl
$VAR1 = [
          200,
          [
            'Content-Type',
            'text/html'
          ],
          [
            'from test'
          ]
        ];

Mypackage.pm

package Mypackage;

sub new {
    my $class = shift;
    my $self = {};
    bless $self, $class;
    return $self;
}

sub test {
    return "from test";
}

1;

Hope this helps, BR.

[Thenothing]

Hello thanos, I want to do the contrary. Get value from main script and retrieve in module. Thanks.

[stevieb]

That's rather backwards. Instead, create a function in the module, and from main, call that function with the required parameters.

[thanos1983]

Hello again Thenothing,

When you say contrary you mean this?

main.pl

#!/usr/bin/perl
use strict;
use warnings;
use Mypackage;

my $object = new Mypackage();
$object->setValue(100);
print $object->getValue() . "\n"; # retrievable from any script

__END__

$ perl main.pl
100

Mypackage.pm

package Mypackage;
use strict;
use warnings;

sub new {
    my $class = shift;
    my $self = {
    _value => shift,
    };
    bless $self, $class;
    return $self;
}

sub getValue {
    my( $self ) = @_;
    return $self->{_value};
}

sub setValue {
    my ( $self, $value ) = @_;
    $self->{_value} = $value if defined($value);
    # return $self->{_value};
}

1;

If not, show an example with words to understand what you mean.

Update: Maybe this? Initialize the class with a value and then update it?

#!/usr/bin/perl
use strict;
use warnings;
use Mypackage;

my $object = new Mypackage(100);
print $object->getValue() . "\n";
$object->setValue(200);
print $object->getValue() . "\n";

__END__

$ perl main.pl
100
200

Hope this helps, BR.

[poj]

Seems very odd but try

BEGIN {
  package main;
  sub test{
    return scalar localtime;
  }
}

use Mypackage;
sub {
  print "OK";
  return [200, ["Content-Type"=>"text/html" ],[Mypackage::test2()]];
};

package Mypackage;

sub test2 {
  ::test();
}
1;

poj

[Thenothing]

Hi there, poj. Thanks for your code, that work, maybe this approach I tried to implement is bad design ? Thanks to everyone.

[Your Mother]

Perl is an incredibly flexible language that gives the power to execute bad designs. Yours is quite bad, especially in a PSGI pipeline where responsibilities are well designed and compartmentalized; and I encourage you to abandon it immediately.

You should not feel bad, though. It's one of the early "intuitive" things a lot of us, especially self-taught programmers, try to do. The other that is almost a rite of passage is using variables as variable names. Working with raw PSGI is quite ambitious. It's not designed to be for direct webwork but for package authors to use as a platform for their higher level kits which are then in turn used for webwork.

If you break down your project into small bites and present them as questions here, you'll probably get terrific advice and code snippets directly on point. Right now you're mostly getting expert advice on how to do things no one but experts even knows how to do because, like wheelies in traffic, it RFC:SHOULDN'T be done. :P

Update: fixed a grammar booger that was bothering me.

[AnomalousMonk]

Interestingly (for some definition of "interesting"), this also works and seems exactly equivalent (update: and reduces worries about phasing of BEGIN blocks, use statements and sub definitions, etc.):

c:\@Work\Perl\monks\Thenothing>perl -le
"use warnings;
 use strict;
 ;;
 use Mypackage;
 ;;
 print Mypackage::test2();
 ;;
 print test();
"
hiya @ Wed Apr 11 12:35:25 2018
hiya @ Wed Apr 11 12:35:25 2018

File Mypackage.pm:

package Mypackage;

use warnings;
use strict;

sub main::test { return 'hiya @ ' . localtime; }

sub test2 { ::test(); }

1;

Oh, and by the way: Don't Do This! Others have suggested much better ways of organizing your code.

[AnomalousMonk]

Further to choroba's reply: "... please, linkify the crosspost link ...":   Please see What shortcuts can I use for linking to other information?