How to dynamically load modules

[Anonymous Monk]

Hi Monks Is there a way to dynamically loading a module. It is like I have a couple of modules having the same functions names in it but doing a totally different job. Now the requirement is that I need to dynamically load the module I need without using a lot of if then else loop. Can any one suggest a way how to do this. Well I have to parse this based on a command line option. Regards Sid

[lachoy]

The CPAN module Class::Factory encapsulates all this for you -- just tell your factory about the different implementations and type associated with each, then pass that type to the factory when you want a new object.

[ikegami]

You can do

$mod = 'My::Module1';
eval "use $mod";

which is the same as

$mod = 'My::Module1';
($mod_file = $mod) =~ s{::}{/}g;
$mod_file .= '.pm';
require $mod_file;
$mod->import if $mod->can('import');

The first two snippet imports the symbols if the module uses Exporter or similar. However, instead of importing, it be safer to do

$mod = 'My::Module1';
eval "require $mod";

$mod->function();

The last snippet requires that function accept an extra initial argument.

[borisz]

I did not understand your description. My best bet is:

eval "require $your_class_name";

[Joost]

Take a look at require.

[tlm]

Just require the modules and don't import the functions that have the same name; invoke them using their fully qualified names. E.g. if both Module1 and Module2 have foo:

require Module1;
require Module2;

Module1::foo();
Module2::foo();

With eval, the above translates to:

my $mod = some_condition() ? 'Module1' : 'Module2';
eval "require $mod; ${mod}::foo()";

TIMTOWTDI: I find the problem description admits too many different interpretations, leading to entirely different solutions; anyway, here's another possible form the solution could take:

use strict;
use warnings;

my $mod = shift;

require "$mod.pm";

eval "$mod->import(); 1" or die;  # modules all export 'foo' by defaul
+t
# eval "$mod->import( 'foo' ); 1" or die;

foo();

Use the commented-out eval instead if you want to limit the functions that are imported.

[jeteve]

Hi . As soon as I understood, you should need something like this: You got your module name into $modName . At runtime, you can do

eval "require $modName";
if( $@ ){
 die("Cannot load $modName : $@");
}