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Moose triggers & method modifiers

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Robert Freimuth via moose
March 29, 2018 13:06
Moose triggers & method modifiers
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I've been learning Moose and I came across unexpected behavior: method modifiers (such as 'after') do not seem to work with attribute triggers. This is an issue because I want a subclass to extend a method that is defined as a trigger in the parent. The issue and one workaround is shown below.
use strict;use warnings;
package Foo;
use Moose;
has 'attrib' => ( is => 'rw', trigger => \&attrib_changed );has 'workaround' => ( is => 'rw', trigger => \&workaround_changed );
sub attrib_changed{    print "  in attrib_changed\n"; # called}
after 'attrib_changed' => sub{    print "    in 'after' attrib_changed\n"; # not called};
sub workaround_changed{    my ( $self ) = @_;    print "  in workaround_changed\n"; # called    $self->not_a_trigger;}
after 'workaround_changed' => sub{    print "    in 'after' workaround_changed\n"; # not called};
sub not_a_trigger{    print "  in not_a_trigger\n"; # called}
after 'not_a_trigger' => sub{    print "    in 'after' not_a_trigger\n"; # called};
my $foo = Foo->new;
print "Calling attrib( 1 ):\n";$foo->attrib( 1 );
print "Calling workaround( 1 ):\n";$foo->workaround( 1 );

Calling attrib( 1 ):  in attrib_changedCalling workaround( 1 ):  in workaround_changed  in not_a_trigger    in 'after' not_a_trigger
I could not find anything in the Moose docs or online that documents this behavior as a known limitation. I'd be surprised if I were the first one to notice it, so it makes me wonder whether I am trying to do something that is best done some other way. Thoughts?

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