This is the first time I see a modifier modifying a method defined in the same class. I've always used modifiers with inheritance or roles, modifying a parent or required method. Nevertheless, you can't wrap a trigger coming from a parent class, either.
That's because the trigger is defined as a code reference, not as a sub name. It means you can modify e.g. a predicate, because it's defined by name, because modifiers redefine a method of the given name.
I see two ways how to wrap a trigger in a more Moosey way: either define a new trigger in the overridden attribute, or define the trigger as a sub that calls a method that you later modify (predicate overriding shown in the example, too):
#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };
{ package My;
use Moose;
has a1 => ( is => 'rw',
trigger => \&a1_changed,
predicate => 'has_attr' );
has a2 => ( is => 'rw',
trigger => sub { $_[0]->a2_changed(@_[ 1 .. $#_ ]) } )
+;
sub a1_changed {
print ref shift, ": a1 changed.\n";
}
sub a2_changed {
print ref shift, ": a2 changed.\n";
}
__PACKAGE__->meta->make_immutable;
no Moose;
}
{ package My::Child;
use Moose;
extends 'My';
has '+a1' => ( trigger => \&a1_changed );
sub a1_changed {
print "Trigger 1 wrapped.\n";
$_[0]->SUPER::a1_changed;
};
around a2_changed => sub {
print "Trigger 2 wrapped\n";
$_[0]->(@_[ 1 .. $#_ ]);
};
around has_attr => sub {
print "Predicate wrapped\n";
};
__PACKAGE__->meta->make_immutable;
no Moose;
}
my $o = 'My'->new;
my $ch = 'My::Child'->new;
$o->a1(2);
$ch->a1(2);
say $o->has_attr;
say $ch->has_attr;
$o->a2(3);
$ch->a2(3);
($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,