Re: Coercion nesting

Dan,

I have to ponder this one, it would basically mean we need to wrap a  
loop around the coerce statement which would keep trying until it  
matched the type. I have concerns about the performance impacts of  
this, and of the possibility of unintended coercions happening since  
types/coercions are essentially global.

We have discussed a (deep_coerce => 1) option for attributes, which  
originally meant that it would coerce inside collections too (coerce  
the elements of an ArrayRef, or of a HashRef), but it could also mean  
"keep coercing until you cant anymore" too.

- Stevan

On Jan 25, 2008, at 2:21 PM, Dan Harbin wrote:

> Below I've included a snippet of my type constraints module where I
> declare my own personal type constraints and coercions.
>
> I'm trying to make it where I can have an accessor of type YAML, where
> I can assign it a string representing a file name.  This file name
> gets coerced into an InputFile, which gets coerced into a YAML.
>
> This gives me an error like so:
> Attribute (file) does not pass the type constraint (YAML) with
> 'config.yml' at Moose/Meta/Attribute.pm line 244
>
> Is there any way to chain or nest the constraints like I've tried  
> below?
>
> Thanks,
> Dan
>
> -------
>
> use Moose::Util::TypeConstraints;
> use IO::File;
> use YAML;
>
> subtype 'InputFile'
>   => as 'Object'
>   => where { $_->isa('IO::Handle') };
>
> coerce 'InputFile'
>   => from 'Str'
>   => via {
>     my $io = IO::File->new();
>     $io->open($_, 'r') or IOException->throw( error => "Unable to open
> file $_: $!" );
>     return $io;
>   };
>
> subtype 'YAML'
>   => as 'Ref';
>
> coerce 'YAML'
>   => from 'InputFile'
>   => via {
>     my $data = do{ local($/); $_->getline };
>     YAML::Load($data);
>   };
>
> 1;