DrSax has asked for the wisdom of the Perl Monks concerning the following question:

I know that i have the code for this somewhere, but I seem to have forgotten how to do this.

I have a constructor for one class, and I want to pass the reference to another subroutine to it. Let's say that I have a Collection, and I want to create it with a specified Sorter.

my $collection = Collection->new({ 'sorter' => Sort::mysorter });

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Collection->new() has the following: 

sub new
{
  my ($self, $options) = @_;
  .  .  .
  $self->{sorter} = /&{$options->{sorter}};
}

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Now, $self->{sorter} is a CODEREF.

Then, when you want to invoke the subroutine you do: 

$self->{sorter}($mystuffToSort);

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I get an "undefined subroutine" error whenever the subroutine lives outside the calling class. Can you help a forgetful old man?

DrSax

Replies are listed 'Best First'.
Re: Passing a reference to a subroutine in a constructor
by tcf22 (Priest) on Aug 22, 2003 at 18:41 UTC
    I think this is what you want(untested) 
    my $collection = Collection->new({ 'sorter' => \&Sort::mysorter });

...

sub new
{
  my ($self, $options) = @_;
  .  .  .
  $self->{sorter} = $options->{sorter};
}

    [download]
    You actually pass the CODEREF into the constuctor, instead of using a soft reference.
[reply]
[d/l]
      I get the same result when I do that. Is the execution of the sort method itself? 
      $self->{sorter}($keys);

      [download]
      Dr. Sax
[reply]
[d/l]
        $self->{sorter}->($keys);

        [download]

        Note the squigglies when de-referencing $self and the round parens when de-referencing the sort routine coderef.

        ------
        We are the carpenters and bricklayers of the Information Age.

        The idea is a little like C++ templates, except not quite so brain-meltingly complicated. -- TheDamian, Exegesis 6

        Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.

[reply]
[d/l]
[select]
Re: Passing a reference to a subroutine in a constructor
by bobn (Chaplain) on Aug 22, 2003 at 18:48 UTC

    After making '/' a '\', it works for me: 

    my $collection = Collection->new({ 'sorter' => Sort::mysorter });

$collection->doit;

package Collection;

sub new
{
  my ($class, $options) = @_;

  $self->{sorter} = \&{$options->{sorter}};
  bless {}, $class;
}

sub doit
{
    print "iam doit\n";
    $self->{sorter}->($mystuffToSort);
}

package Sort;

sub mysorter
{
    print "iam mysorter\n";
}

    [download]

    On the other hand, I'm not sure what you meant by "out of the scope of the calling package".

    All code given here is UNTESTED unless otherwise stated.

    --Bob Niederman, http://bob-n.com
[reply]
[d/l]
      Your approach only seems to work for me when the package is in the same file. All of our classes/packages live in seperate files. Could that have an impact?

      DrSax

[reply]
        Just wondering: have you actually -use-d or -require-d the other packages?

        I realize this is equivalent to asking whether the computer is plugged in, but you never know ;-)

        Liz

[reply]
Re: Passing a reference to a subroutine in a constructor
by CombatSquirrel (Hermit) on Aug 22, 2003 at 18:42 UTC
    I suppose you rather mean 
    my $collection = Collection->new({ 'sorter' => \&Sort::mysorter });

sub new
{
  my ($self, $options) = @_;
  .  .  .
  $self->{sorter} = $options->{sorter};
}

    [download]
    As to my knowledge, this should work (notice the slash - backslash difference).
    Cheers, CombatSquirrel.
[reply]
[d/l]
      To all who noted the backslash, I have the correct slash direction in my real code. The code I posted was typed in lovingly by hand into the web page since I can't cut and paste between the computer I develop on (Sparcstation) and the one I Monk on (Windows). It doesn't seem to matter whether I use the form: 
      my $collection = Collection->new({ 'sorter' => Sort::mysorter });

sub new
{
  my ($self, $options) = @_;
  .  .  .
  $self->{sorter} = \&$options->{sorter};
}

      [download]
      or... 
      my $collection = Collection->new({ 'sorter' => \&Sort::mysorter });

sub new
{
  my ($self, $options) = @_;
  .  .  .
  $self->{sorter} = $options->{sorter};
}

      [download]
      When I get to : 
      $self->sorter($stuffToSort);

      [download]
      or $self->sorter->($stuffToSort); I get the same results.

      DrSax

[reply]
[d/l]
[select]

        here it is in separate files works fine: 

        [bobn@trc2:/home/bobn/misc]# cat subref.pl
#!/usr/bin/perl -w

use lib q/./;

use Collection;
use Sort;

my $collection = Collection->new({ 'sorter' => \&Sort::mysorter });

$collection->doit('here is something');

[bobn@trc2:/home/bobn/misc]# cat Collection.pm 
        package Collection;

        my $self = {}; 
        sub new
        {
                my ($class, $options) = @_;
                $self->{sorter} = $options->{sorter};
                bless $self, $class; 
        }

        sub doit
        {
                my ($self, $stuffToSort ) = @_;
                print "in doit: $stuffToSort\n";
                $self->{sorter}->($stuffToSort);
                print "in doit: $stuffToSort\n";
        }
        1;
[bobn@trc2:/home/bobn/misc]# cat Sort.pm 
package Sort;

sub mysorter
{
        print "in mysorter, @_\n";
} 
1;
[bobn@trc2:/home/bobn/misc]# ./subref.pl
in doit: here is something
in mysorter, here is something
in doit: here is something

        [download]

        All code given here is UNTESTED unless otherwise stated.

        --Bob Niederman, http://bob-n.com
[reply]
[d/l]

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