[Dbix-class] overriding create [was role of result class? ]

[Richard Jolly]

Jess Robinson wrote:

> On Tue, 7 Mar 2006, Richard Jolly wrote:
> 
> > I'm trying to understand the role of the result_class, and 
> I have what 
> > I think are naive questions.
> >
> > In a schema with
> >
> >   My::Schema::Artist
> >
> >   ...
> >
> >   my $schema->resultset('Artist')->search();
> >   My::Artist->search();
> >
> > Are the last two lines identical? Why is the first the 
> preferred syntax?
> 
> Whether those two are identical or not, depends on how you 
> connected, if you just do;
> 
> My::Schema->connection('dbi:Foo' .. );
> 
> Then there is just one global connection, and you can call 
> search on your class names, if however you  use:
> 
> my $schema = My::Schema->compose_connection, or ->connect,
> 
> then the information about the connecion/DB is stored in the 
> $schema object (in $schema->storage), and My::Artist->search 
> will not work at all.
> 
> > Secondly, when over riding resultset methods for a specific class I 
> > believe the new methods get defined in My::Schema::Artist. But you 
> > could put them in My::Artist as well, and they would just 
> sit slightly 
> > higher up the MRO. Does anyone actually put methods in the result 
> > class file?
> 
> No, adding methods to My::Schema::Artist or My::Artist will 
> only make them available to Row objects (DBIx::Class::Row).
> 
> The difference is this:, If you run a search in scalar 
> context, what you get is a ResultSet object, which will not 
> have any of the methods you put in your individual table 
> classes (My::Artist etc.), but does have convenience methods 
> like ->count (how many items were returned) and so on. 
> Calling ->next on that result set, or calling search in list 
> context, will get you Row objects, which will each represent 
> a row of the result, and will be inherited from your 
> My::Artist/table classes, and thus inherit those methods.
> 
> So if you want to add methods to a search result as a whole, 
> you need to create your own result_class ..
> 
> I hope that makes sense,
> 
> Jess

Thanks. It makes sense, but it doesn't quite jibe with my experience.
I've made the problem more concrete...

I'm trying to override the create() method of a particular class, so
that it creates two other related objects. But using the
$schema->resultset('Foo')->create syntax bypasses my overriden method.
Is that expected?

If I define new() instead it does get called - but since I'm inserting
rows with create_related I think it needs to be in create. The method in
question looks something like:

sub create {
  my $row = shift()->next::method(@_);
  $row->create_related(..);
  $row
}



Here is a sample schema that shows create() being bypassed. Any comments
welcome.

==> ./create.pl <==
use strict;
use warnings;

use My::Setup;

my $schema = My->schema;

print "with schema->resulset\n";
$schema->resultset('Artist')->create({artistid => $$, name => 'Bill'});

print "with schema->class (resolves to class name)\n";
$schema->class('Artist')->create({artistid => $$+1, name => 'Bill'});

print "with My::Artist\n";
My::Artist->create({artistid => $$+2, name => 'Bill'});

__END__

Output is:

with schema->resulset
Found Artist new
with schema->class (resolves to class name)
Found Artist create
Found Artist new
with My::Artist
Found Artist create
Found Artist new

So the My::Schema::Artist::create() is not called when using the
resultset syntax.


==> ./db/create.sql <==
create table artist (
	artistid integer,
	name text,
	primary key( artistid )
);

==> ./lib/My/Schema/Artist.pm <==
package My::Schema::Artist;

use strict;
use warnings;

use base qw/DBIx::Class/;

__PACKAGE__->load_components( 'Core' );

__PACKAGE__->table('artist');
__PACKAGE__->add_columns(qw/artistid name/);
__PACKAGE__->primary_key('artistid');

sub new { print "Found Artist new\n"; shift()->next::method(@_);  };
sub create { print "Found Artist create\n"; shift()->next::method(@_);
};

1;

==> ./lib/My/Schema.pm <==
package My::Schema;

use strict;
use warnings;

use base qw/DBIx::Class::Schema/;

__PACKAGE__->load_classes();

1;

==> ./lib/My/Setup.pm <==
package My::Setup;

use strict;
use warnings;

use My::Schema;

my $dsn = 'dbi:SQLite:db/artist.db';

My::Schema->compose_connection( My => $dsn);

1;


Any comments welcome.

Thanks, Richard

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