Re: Moose Question

Chris,

Actually that code I pasted below has some issues with it, I have  
converted it into an example test in Moose though, so here is the  
corrected (and working) version:

http://code2.0beta.co.uk/moose/svn/Moose/trunk/t/200_examples/ 
008_record_set_iterator.t

- Stevan

On Mar 20, 2008, at 11:38 AM, Stevan Little wrote:
> Chris,
>
> On Mar 19, 2008, at 5:22 PM, Christopher Brown wrote:
>> I do have follow-up questions, though.  Suppose I want to generate  
>> those
>> plain old methods dynamically.  Is there a simple, moose way to do  
>> this in
>> the BUILD subroutine.   On e way to accomplish this is to assign an
>> anonymous subroutine to a glob.  Like this:
>
> The BUILD method runs every time an object is created (per- 
> instance) and by altering the symbol table you are adding a method  
> to the class itself. If the method you add is a closure around a  
> $row (which it seems that is what you are going for) you will only  
> be able to use one instance of this class at a time, otherwise the  
> method you add will override one another.
>
>> package My::App;
>>
>> use Moose;
>> has name => ( is => 'rw', isa=>'Str' );
>>
>> sub BUILD {
>>         **__PACKAGE__::method = sub { print "hello world\n"; } ;*
>> }
>>
>> package main;
>> my $app = My::App->new( { name => 'Moose' } );
>> $app->method;
>>
>>
>> But I don't want to do that.  I want to do it the Moose way.
>
> As I said above, this is not really a good idea, but the Moosey way  
> to do it would be:
>
> sub BUILD {
>     my $self = shift;
>     $self->meta->add_method('method' => sub { ... });
> }
>
> This is documented in Class::MOP::Class.
>
>> I can hear you ask, but why would you want to do that?  Well  
>> suppose, I
>> create an object that wraps a query.  If I can iterate over the  
>> record set I
>> can replace the data slot with the new record and still named  
>> methods that
>> act as accessors to the record.  This beats the snot out of trying to
>> instanciate a row object for each record.
>
> I think, if I understand what you are trying to do correctly, you  
> should do something like this:
>
> (WARNING: this is completely untested code, but it **should** work)
>
> package RecordSetIterator;
> use Moose;
>
> has 'record_set' => (
>     is  => 'ro',
>     isa => 'RecordSet',
> );
>
> # list the fields you want to
> # fetch from the current record
> my @fields = qw[
>     first_name
>     last_name
> ];
>
> has 'current_record' => (
>     is      => 'ro',
>     isa     => 'Record',
>     lazy    => 1,
>     default => sub {
>         my $self = shift;
>         $self->record_set->next() # grab the first one
>     },
>     trigger => sub {
>         my $self = shift;
>         # whenever this attribute is
>         # updated, it will clear all
>         # the fields for you.
>         $self->$_() for map { '_clear_' . $_ } @fields;
>     }
> );
>
> # define the attributes
> # for all the fields.
> has $_ => (
>     is      => 'ro',
>     # make sure they have a clearer ...
>     clearer => ('_clear_' . $_)
>     lazy    => 1,
>     default => sub {
>         my $self = shift;
>         # fetch the value from
>         # the current record
>         $self->current_record->$_();
>     },
> ) for @fields;
>
> sub get_next_record {
>     my $self = shift;
>     $self->current_record($self->record_set->next());
> }
>
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