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

I'm having a problem with Class::MethodMaker object_list forwarded methods. Maybe I just can't get the syntax right. Can anyone can point me to a working code example or provide some insight? Or maybe ideas about peeking into the C::MM generated methods? My broken code and output follow the POD excerpt.

From POD:

object_list
Functions like list, but maintains an array of referenced objects in each slot. Forwarded methods return a list of the results returned by maping the method over each object in the array.
Arguments are like object.
use strict;

use Class::MethodMaker "-sugar";

package MyPackage::Item;
make methods
    new_hash_init => 'new',
    get_set => [qw/ name /],
; # make methods


package MyPackage::List;
make methods
    new_hash_init => 'new',
    object_list   => [
       MyPackage::Item => {
          slot => 'items',
          comp_mthds => [qw/ name /],
       },
    ],
;

package main;

use Data::Dumper;

my $list = MyPackage::List->new();
$list->items_push( MyPackage::Item->new(name=>'test1') );

print Dumper($list);

# POD says this should return a list from a map 
# of the forwarded methods over all objects in 
# the list, but I can't get it to work!
print $list->items->name;

[download]
Output: 
$VAR1 = bless( {
                 'items' => [
                              bless( {
                                       'name' => 'test1'
                                     }, 'MyPackage::Item' )
                            ]
               }, 'MyPackage::List' );
Can't call method "name" on unblessed reference at test.pl line 32.

[download]
--
The ability to destroy planets is insignificant next to the power of the Deacon Effect.

Replies are listed 'Best First'.
How to 'Do The Work' (was Re: Class::MethodMaker object_list help needed)
by Solo (Deacon) on Feb 03, 2003 at 19:35 UTC
    Since I hate questions without answers and nodes without conclusions--here are my findings.

    I was being an idiot. However, I think the manner in which I discovered this Simple Truth is worthwhile reading. First, the answer.

    In the example code above, the correct syntax for calling the forwarded name method for the MyPackage::List object is as follows.

    print $list->name;  # NOT: print $list->items->name

    [download]

    Of course, this seems obvious with hindsight. It's a method of the $list object! I think I was trapped in a VB mindset and couldn't see the obvious Perlish use... or something.

    Anyway, on to the important bit.

    How I figured this out--aka How to 'Do The Work'

    1. I read the POD.
    2. I read the POD again.
    3. I looked at the module source*
    4. I used Super Search to look for "MethodMaker".
    5. I used Google to look for "MethodMaker".
    6. I spent a long time finding every pod2html mirror in existence.
    7. I got smart and Googled the comp.lang.perl groups.
    That's when I found a nice thread about exploring the symbol table--and knew that was where I could find the name (hence, usage) of the Class::MethodMaker method. Dominus posted the code I used.

    Moreover, I found a wealth of other information. For instance, "-sugar" probably shouldn't be used... and a long list of reasons that I should use Class::MakeMethods instead.

    Now, if I could only get Class::MakeMethods 1.006 to build under Win32... **sigh** ...back to work!

    --
    * The point in time that I scratched my head and called for backup.

    May the Source be with you.

[reply]
[d/l]
[select]
      For what it's worth, the problem with Class::MakeMethods 1.006 on Windows was just a "make test" failure (see node 276489) -- the module itself worked correctly -- and that problem should be fixed in the new 1.008 release.
[reply]

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