package C;

use strict;

use base qw(model type);
1;
__END__
$ perl -e 'use C'
Base class package "model" is empty.
    (Perhaps you need to 'use' the module which defines that package f
+irst.)
 at C.pm line 5
BEGIN failed--compilation aborted at C.pm line 5.
[download]

Working code to scrutinize would help to help.

Apart from that, you might want to have a look at Spiffy.

package A;
use Spiffy -Base;
use strict;
field $_ for qw(id name);
sub new { bless {}, $self }
[download]

package B;
use A -Base;
use strict;
field $_ for qw(addr phone city);
sub new { bless {}, $self }
[download]

package C; 
use A -Base;
use strict;
field $_ for qw(model type);
sub new { bless {}, $self }
[download]

#!/usr/bin/perl
use strict;
use B;
use C;
use Data::Dumper; $Data::Dumper::Indent = 1;

my $foo = new C;
$foo->id(123);
$foo->name("thingy");
$foo->model("Z80");

my $bar = new B;
$bar->id(456);
$bar->city("Lhasa");
$bar->name("kouxuan");

print Dumper($foo);
print Dumper($bar);
__END__
$VAR1 = bless( {
  'model' => 'Z80',
  'name' => 'thingy',
  'id' => 123
}, 'C' );
$VAR1 = bless( {
  'city' => 'Lhasa',
  'name' => 'kouxuan',
  'id' => 456
}, 'B' );
[download]

Spiffy rocks ;-)

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

Yes, your right. It's mistake. It should be:

use base qw(A);
use fields qw(model type);
[download]

---
Michael Stepanov aka nite_man

It's only my opinion and it doesn't have pretensions of absoluteness!

If I use class names like ClassA and ClassB (because B is a system class), everything seems to work OK for me. I have had similar problems to those you describe when I tried to put multiple packages in the same file with nontrivial inheritance relationships.

Here's the code I tested:

package ClassA;

use strict;

use base qw(fields);
use fields qw(id name);

sub new {
  my $class = shift;
  $class->SUPER::new();
}

sub getclass
{
  my $self = shift;
  return ref($self);
}

1;
[download]

package ClassB;

use strict;

use base qw(ClassA);
use fields qw(addr phone city);

use ClassC;

sub addC
{
  my $self = shift;
  $self->{c} = ClassC->new();
}
1;
[download]

package ClassC;

use strict;

use base qw(ClassA);
use fields qw(model type);

sub addB
{
  my $self = shift;
  $self->{b} = ClassB->new();
}
1;
[download]

#!/usr/bin/perl -l
# Test program
use ClassA;
use ClassB;
use ClassC;

my $a = ClassA->new();
my $b = ClassB->new();
my $c = ClassC->new();

print $a->getclass();
print $b->getclass();
print $c->getclass();

$b->{name} = 'bee';
print $b->{name};

$c->{name} = 'see';
print $c->{name};

$b->{city} = 'wok';
print $b->{city};

$c->{model} = 't';
print $c->{model};
[download]

Hi sgifford, Probably you're right. The problem with nontrivial inheritance relationships. But how to avoid it (to rebuild whole application is not appropriate way :))?

---
Michael Stepanov aka nite_man

It's only my opinion and it doesn't have pretensions of absoluteness!

I only had this problem when I put multiple classes with inheritance relationships in the same file; putting each class in its own file solved the problem.

--
sgifford's Web page