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

Trying to use autoload for the first time ;-)

I can create a "sub AUTOLOAD" in main:: to dynamically call a function and it works cool!

Now, I want to move the stuff into a package called foo::

But, the docs say (I think) that there can only be one sub AUTOLOAD defined in each package...I was thinking I could use BEGIN in my package to create the main::AUTOLOAD to do what I want...but this assumes that the user hasn't already created a main::AUTOLOAD....I am stuck

(pseudo code) 
package main;
  myfunc(1,2,3); # I want to redirect to foo::myfunc()

  sub AUTOLOAD { 
    if $caller eq "foo"
       foo::myfunc(@_);
  }  
  # Any way to get rid of the main::autoload and somehow
  # handle it in the foo package ???  Or is there a way 
  # to override AUTOLOAD in my package using BEGIN or ???

[download]

thanks!!!

uc(autoload) in title - dvergin 2002-05-11

Replies are listed 'Best First'.
Re: autoload and packages
by svad (Pilgrim) on May 11, 2002 at 09:26 UTC
    you could either use Exporter module, or, even simpler, following approach: 
    package mypackage;
sub my_lovely_autoload_for_main {
  # bla bla bla
  print STDERR "[@_]\n";
}
*::main::AUTOLOAD = \&::mypackage::my_lovely_autoload_for_main;

package main;
fjkre('wdw');

    [download]
    Vadim

    PS. Checking for existing main::AUTOLOAD and calling at appropriate time is left as exercise for reader :)

[reply]
[d/l]
      Thanks, I kinda get it...but if there is a main::AUTOLOAD, do I have to "rename" it? As it seems "*::main::AUTOLOAD = \&::mypackage::my_lovely_autoload_for_main;" will override it and then I can't call the original main::AUTOLOAD... Am I missing something?
[reply]
        okay, you decided not to do exercise for a reader :)
        Let me give you my code for example for a reader: 
        BEGIN{
  if (exists $::{AUTOLOAD}) {
    print "exisa\n";
  } else {
    print "no-exisa\n";
  }
}
sub AUTOLOAD{}
BEGIN{
  if (exists $::{AUTOLOAD}) {
    print "exisa\n";
  } else {
    print "no-exisa\n";
  }
}

        [download]
        Sorry for not clearing it for cleverness, I'm drunk now :)
        but I checked it, it works!
[reply]
[d/l]
Re: autoload and packages
by TheHobbit (Pilgrim) on May 11, 2002 at 09:54 UTC

    Hi,
    No need to use AUTOLOAD here, simply use Exporter as in 

    package foo;
use Exporter;
use vars qw(@ISA @EXPORT);
@ISA=qw(Exporter);
@EXPORT=qw(myfunc);
sub myfunc {
  #something clever;
}

package main;
use foo; #imports myfunc, so that now
         # main::myfunc is an alias for
         # foo::myfunc

myfunc(1,2,3); #calls foo:myfunc(1,2,3)

    [download]

    Autoload is usefull for other things, like automatic generation of functions.

    Cheers

    Leo TheHobbit
    Update minor typos corrected, thanks to gmax.
[reply]
[d/l]
      Thanks, but my function name is dynamic...I guess the "example" was too simplistic...Vadim's approach sounds like a bit of work, but would work...
[reply]
Re: AUTOLOAD and packages
by strat (Canon) on May 13, 2002 at 10:14 UTC
[reply]
Re: AUTOLOAD and packages
by svad (Pilgrim) on May 15, 2002 at 16:47 UTC
    if we'll see into perlref.pod and search for substring {CODE} and read around a bit, then we'll calmly understand that we're able to do following trick: 
    use strict;

package main;

sub AUTOLOAD {
  return 'old-main-autoload';
}

package mypackage;

# let's capture that ::AUTOLOAD
my $aasub = *{$::{AUTOLOAD}}{CODE};

# now let's, as we decided earlier, have it overloaded
*::AUTOLOAD = sub {
  print "do first\n";
  #now call old one and print that returned value inside '[]'
  print '[', $aasub->(), "]\n";
  print "do last\n";
};

package main; # again

flurfish_sub();

    [download]
    in my case output is 
    do first
[old-main-autoload]
do last

    [download]
    But my personal advice - you're moving to C-like area or even assembler code catching area when you will really soon will complicate logic.
    I think when you will see that code in your program then it is a good signal to redesign your code.
    :)

    Best wishes,
    Vadim.

[reply]
[d/l]
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