dynamic loading

[Arshavir Grigorian <gr...@gmail.com>]

Hi,

I am wondering if anyone has experience with a framework for
dynamically loading certain modules into an application and executing
certain code based on whether a certain module is loaded (available or
not). By "dynamically", I do not mean loading run-time, only being
able to safely exclude certain modules at startup. One place this
could come in handy is when selling an app to 2 clients of whom one
has purchased all the functionality and the other has not, and you
don't want to give them certain module(s). I am guessing one could
accomplish this by using a macro processor (m4) to preprocess Perl
code before it's "released", but it would probably be somewhat
painful.

I'd love to hear what others have done in similar situations. Thanks in advance.


Arshavir

Re: dynamic loading

[Arshavir Grigorian <gr...@gmail.com>]

Thanks for all the posts.

Re: dynamic loading

[James Smith <js...@sanger.ac.uk>]

For the project I work on many of our Modules derive from a common
Root module which contains the following dynamic_use call which is
exactly the same as a use line - but does not fail fatally if the
module isn't there - it also nicely means that the code isn't
loaded up front (as if all blocks of code were included with a
normal use line)... it seems to work OK for the project (which
has a nice plugin system)

our $failed_modules;

sub dynamic_use {
  my( $self, $classname ) = @_;
  unless( $classname ) {
    my @caller = caller(0);
    my $error_message = "Dynamic use called from $caller[1] (line
$caller[2]) with no classname parameter\n";
    warn $error_message;
    $failed_modules->{$classname} = $error_message;
    return 0;
  }
  if( exists( $failed_modules->{$classname} ) ) {
  #  warn "EnsEMBL::Web::Root: tried to use $classname again - this has
already failed $failed_modules->{$classname}";
    return 0;
  }
  my( $parent_namespace, $module ) = $classname =~/^(.*::)(.*)$/ ? ($1,$2)
: ('::',$classname);
  no strict 'refs';
  return 1 if $parent_namespace->{$module.'::'} && %{
$parent_namespace->{$module.'::'}||{} }; # return if already used
  eval "require $classname";
  if($@) {
    warn "EnsEMBL::Web::Root: failed to use
$classname\nEnsEMBL::Web::Root: $@" unless $@ =~/^Can't locate /;
    $parent_namespace->{$module.'::'} = {};
    $failed_modules->{$classname} = $@ || "Unknown failure when
dynamically using module";
    return 0;
  }
  $classname->import();
  return 1;
}

sub dynamic_use_failure {
  my( $self, $classname ) = @_;
  return $failed_modules->{$classname};
}



On Mon, 21 Aug 2006, John ORourke wrote:

> Arshavir Grigorian wrote:
>
> > I am wondering if anyone has experience with a framework for
> > dynamically loading certain modules into an application and executing
> > certain code based on whether a certain module is loaded (available or
> > not). By "dynamically", I do not mean loading run-time, only being
> > able to safely exclude certain modules at startup. One place this
> > could come in handy is when selling an app to 2 clients of whom one
> > has purchased all the functionality and the other has not, and you
> > don't want to give them certain module(s). I am guessing one could
> > accomplish this by using a macro processor (m4) to preprocess Perl
> > code before it's "released", but it would probably be somewhat
> > painful.
>
>
> I'm just finishing a plugin architecture which dynamically loads
> available plugins, but in doing so I found some useful CPAN modules:
>
> Module::Optional - exactly what you're after
> Module::Pluggable - very flexible plugin/optional module manager
>
> hth,
> John
>
>

Re: dynamic loading

[John ORourke <jo...@o-rourke.org>]

Arshavir Grigorian wrote:

> I am wondering if anyone has experience with a framework for
> dynamically loading certain modules into an application and executing
> certain code based on whether a certain module is loaded (available or
> not). By "dynamically", I do not mean loading run-time, only being
> able to safely exclude certain modules at startup. One place this
> could come in handy is when selling an app to 2 clients of whom one
> has purchased all the functionality and the other has not, and you
> don't want to give them certain module(s). I am guessing one could
> accomplish this by using a macro processor (m4) to preprocess Perl
> code before it's "released", but it would probably be somewhat
> painful.


I'm just finishing a plugin architecture which dynamically loads 
available plugins, but in doing so I found some useful CPAN modules:

Module::Optional - exactly what you're after
Module::Pluggable - very flexible plugin/optional module manager

hth,
John

Re: dynamic loading

["Philip M. Gollucci" <pg...@p6m7g8.com>]

Arshavir Grigorian wrote:
> Hi,
> 
> I am wondering if anyone has experience with a framework for
> dynamically loading certain modules into an application and executing
> certain code based on whether a certain module is loaded (available or
> not). By "dynamically", I do not mean loading run-time, only being
> able to safely exclude certain modules at startup. One place this
> could come in handy is when selling an app to 2 clients of whom one
> has purchased all the functionality and the other has not, and you
> don't want to give them certain module(s). I am guessing one could
> accomplish this by using a macro processor (m4) to preprocess Perl
> code before it's "released", but it would probably be somewhat
> painful.
Actually I dont' think the m4 idea is so bad, you could probably just have it stub out the packages
package A;
1;

and change your code to do ::can() or ->can() as appropriate.

I can't think of another way, that will keep the "conditional" code shared for those that bought it all.





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