Force coercion in Moose - perl

Question

I want to modify an attribute's value every time it is set, no matter if it is done within constructor or by a 'writer'(i don't use 'builder' or 'default' in that case). Basically the attribute(not necessary 'Str' type) is passed to the constructor and in some cases I want to modify its value after that, but in every scenario I want to do some regexp on it (for example).
My first approach was to use a BUILDARGS and around method, both of would use the same regex function, but then I wonder about coercion. The only problem is I don't know how to create a subtype/type definition that will force coercion no matter what.
For example:
package Foo;
use Moose::Util::TypeConstraints;
subtype 'Foo::bar' => as 'Str';
coerce 'Foo::bar'
=> from 'Str'
=> via {
$_ =~ s/some_stuff//g;
$_ =~ s/other_stuff//g;
$_ =~ s/some_other_stuff//g;
};
has 'bar' => (isa => 'Foo:bar', coerce => 1);
I don't want to define subtype/type with 'where' clause like
subtype 'Foo::bar' => as 'Str' => where {$_ !~ /some_stuff/ && $_ !~ /other_stuff/ && ... };
because it seems tedious to me.
Edit: I'm looking for a comprehensive solution I could use not only with 'Str' type attributes but also 'ArrayRef', 'HashRef' etc.

Answer 1

Sounds like you want a trigger.
package Foo;
use Moose;
has 'bar' => (
is => 'rw',
isa => 'Str',
trigger => sub {
my ( $self, $value, $old_value ) = #_;
say 'in trigger';
# prevent infinite loop
return if $old_value && $old_value eq $value;
my $original_value = $value;
$value =~ s/some_stuff//g;
$value =~ s/other_stuff//g;
$value =~ s/some_other_stuff//g;
# prevent infinite loop
return if $value eq $original_value;
say '... setting new value';
$self->bar($value);
},
);
package main;
my $foo = Foo->new( bar => 'foo some_stuff and other_stuff and some_more_stuff' );
say $foo->bar;
I want to modify an attribute's value every time it is set, no matter
if it is done within constructor or by a 'writer'(i don't use
'builder' or 'default' in that case)
This is exactly what a trigger does. The doc says almost verbatim what you asked for:
NOTE: Triggers will only fire when you assign to the attribute, either in the constructor, or using the writer. Default and built values will not cause the trigger to be fired.
Edit: There was a bug in the inifite loop detection. It now works and will stop on the second invocation. I left debug output in to demonstrate.
in trigger
... setting new value
in trigger
foo and and some_more_stuff