Re: attribute w/ coerce and trigger - trigger arguments

Thanks Stevan,

I'm impressed by the quick turnaround, and I look forward to trying  
out the new release.

Charles Alderman
aldermania.com

----- Original Message -----
From: Stevan Little <[email protected]>
Sent: Sat, 12 Apr 2008 23:55:24 -0400
Re: Re: attribute w/ coerce and trigger - trigger arguments



> Charles,
>
> This bug has been fixed in svn
> (http://code2.0beta.co.uk/moose/svn/Moose/trunk/) and will be in the
> next release (coming soon, probably this week sometime).
>
> - Stevan
>
> On Apr 9, 2008, at 2:40 PM, Charles Alderman wrote:
>> Hello,
>>
>> Just started using Moose (love it).  I recently spent a little time  
>>  struggling through an issue with trigger arguments for a coerced   
>> attribute.  So, I thought I'd post what I found here in case anyone  
>>  else runs into it.
>>
>> Actually, I'm not sure if I found an undocumented feature of Moose,  
>>  or if it's a bug.  The docs say that a trigger is passed an  
>> updated  value of the attribute.  What happens is that if the  
>> attribute has  a coercion, the argument passed to the trigger  
>> hasn't been coerced.   So, technically, the argument isn't an  
>> updated value.  (At least,  that's where my confusion came from.)
>>
>> The coerced value is still available to the trigger through the   
>> attribute's accessor, so maybe having the non-coerced value also   
>> available is for the best.
>>
>> For clarification, I included an example.
>>
>> Thanks,
>> Charles Alderman
>> aldermania.com
>>
>> Versions:
>> Moose - 0.40
>> Class::MOP - 0.54
>>
>> --
>>
>> From the Moose perldoc:
>>
>> The trigger option is a CODE reference which will be called after   
>> the value of the attribute is set. The CODE ref will be passed the   
>> instance itself, the **updated value** and the attribute   
>> meta-object (this is for more advanced fiddling and can typically   
>> be ignored).
>>
>> --
>>
>> Here's an example:
>> #This example is based on: Schwartz, R.L. "The Moose is Flying   
>> (part 2)". LinuxMag Column 95 (Jul 2007)
>>
>> package Mortgage;
>>
>> use Moose;
>> use Moose::Util::TypeConstraints;
>>
>> use DateTime;
>> use DateTime::Format::DateManip;
>> use Date::Manip;
>> Date_Init( 'TZ=US/Eastern' );
>>
>> subtype 'DateTime'
>>  => as 'Object'
>>  => where { $_->isa('DateTime') };
>>
>> coerce 'DateTime'
>>  => from 'Str'     => via {   
>> DateTime::Format::DateManip->parse_datetime($_) }
>>  => from 'HashRef' => via { DateTime->new(%$_) };
>>
>> has 'closing_date' => (
>>  is => 'rw',
>>  isa => 'DateTime',
>>  coerce => 1,
>>
>>  trigger => sub {
>>    my ( $self, $val, $meta ) = @_;
>>    print $self->closing_date->isa('DateTime') ? 'yes' : 'no';  # yes
>>    print $val->isa('DateTime')                ? 'yes' : 'no';  # no???
>>  }
>> );
>>
>> 1;
>>
>> package main;
>>
>> my $mtg = Mortgage->new( closing_date => 'yesterday' );
>> print $mtg->closing_date->isa('DateTime') ? 'yes' : 'no';  # yes
>>
>>