Referring to a module with a string in Perl

Question

I have a string with a module name and need to use this to instantiate an object. How is this best done? I am looking for something like

foo.pl

#!/usr/bin/perl
use strict;
use Bar;

my $module = "Bar";
my $obj = {$module}->new(); # does not work

$obj->fun (123);

Bar.pm

package Bar;
use strict;
sub new
{
    my $self = {};
    return bless $self;
}

sub fun
{
    my ($self, $arg);
    print "obj $self got arg $arg\n";
}

Answer 1

You're overcomplicating. $module->new works just fine on its own with no {braces}:

$ perl -MXML::Simple -E 'use strict; my $foo = "XML::Simple"; my $obj = $foo->new; say $obj'
XML::Simple=HASH(0x9d024d8)

Answer 2

Besides the provided notes about unnecessary braces, you could be interested in Class::MOP or Class::Load (for more recent code), especially the load_class() subroutine, for a more dynamic loading of modules/classes.

Answer 3

You have to use the Perl function eval. You also have to use ref to get the name of a perl Object. But first of all your foo method isn't taking the arguments, here is a corrected version :

package Bar;
use strict;
sub new
{
    my $self = {};
    return bless $self;
}

sub fun
{
    my ($self, $arg) = @_;
    print "obj ".ref($self)." got arg $arg\n";
}

1;

Here is the test script :

#!/usr/bin/perl
use strict;
use Bar;

my $module = "Bar";
my $obj = eval {$module->new()};

$obj->fun (123);

Output : obj Bar got arg 123