Hello monks, I'm back with a Moose question that's causing me some head scratching. I have the following code:

package Foo;

use Moose;

has 'y' => (
    is => 'Num',
    is => 'rw'
);

has 'x' => (
    is => 'Num',
    is => 'rw'
);

sub init_y {
    my ($self, $value) = @_;
    $self->y(sqrt($self->x));
}

sub BUILD {
    my ($self) = @_;

    print STDERR "Foo::BUILD running\n";
    $self->init_y;
}

1;

[download]

And:

package Foo::Bar;

use Moose;
extends 'Foo';

before 'BUILD' => sub {
    my $self = shift;
    print STDERR "Foo::Bar before BUILD running\n";
    $self->x(25);
};

1;

[download]

And my test script:

use lib '.';
use Foo::Bar;

use Data::Dumper;

my $o = Foo::Bar->new;

print STDERR Dumper($o);

[download]
My output is this: 
plxc16479> ex.pl
Foo::BUILD running
Use of uninitialized value in sqrt at Foo.pm line 17.
Foo::Bar before BUILD running
Foo::BUILD running
$VAR1 = bless( {
                 'y' => '5',
                 'x' => 25
               }, 'Foo::Bar' );

[download]

So, my question is...why am I seeing Foo::BUILD execute twice? My guess is that Foo::Bar is inheriting Foo's BUILD method...meaning there is now Foo::Build and Foo::Bar::BUILD. The base Foo::Build executes. Since Foo::Bar has a before BUILD modifier, and an inherited BUILD method, Foo::Bar before BUILD is executed before the subclass Foo::Bar::BUILD...but after Foo::BUILD has already done its thing.

Assuming this is the case, how do I get the behavior that I want? The idea is that Foo::Bar can modify the way Foo initializes by presetting 'x' to a particular value. However, I seem unable to do this with a sub class before Foo::BUILD executes. Here, that results in a warning but it can definitely result in problems in real code.

In reply to Moose and BUILD by tj_thompson

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