On 20 April 2015 at 07:00, Andrew Hicox <and...@hicox.com> wrote:
> This seems like I’d just need to declare a writer sub for the attribute,
> do my logic in there, then set the attribute value or throw an error, right?
>
> Why doesn't this work?
>
> package Bogus {
> use Moose;
> has ‘value’, is => “rw”, writer => “_value”, isa => “Num”;
> sub _value {
> my ($self, $value) = @_;
> ## insert some logic here
> $self->value($value);
> return(1);
> }
> }
>
> use Bogus;
> my $a = new Bogus(value => 1);
>
>
The initial mistake I believe you made was thinking that the argument to
writer was intended to be a "I'll create this sub, Moose can use it".
Whereas that argument in this case is "Moose, create me a writer called
_value".
So the RHS of that token is intended for more external interfaces, eg:
---
has value => ( is => 'rw', writer => "set_value" , reader => "get_value");
...
$object->set_value( $arg );
$object->get_value(); # returns $arg
---
so:
$writer_sub -> internal attribute store
$reader_sub <- internal attribute store
$writer_sub and $readersub can sometimes be the same sub, which is the
default case with "is => rw".
For comparion, see: "is => raw", where $object->value won't exist.
--
Kent
*KENTNL* - https://metacpan.org/author/KENTNL
