[EP-tech] Re: Understanding how data objects link

[sf2 at ecs.soton.ac.uk (Sebastien Francois)]

Hi Ian,

Your problem may come from 
perl_lib/EPrints/MetaField/Subobject.pm::get_value


         my $ds = $parent->get_session->dataset( $self->get_property( 
"datasetid" ) );

         my $searchexp = $ds->prepare_search();

         if( $ds->base_id eq "document" )
         {
                 $searchexp->add_field(
                         $ds->field( "eprintid" ),
                         $parent->id
                 );
         }
         elsif( $ds->base_id eq "saved_search" )
         {
                 $searchexp->add_field(
                         $ds->field( "userid" ),
                         $parent->id
                 );
         }
         # ETC...


(you should upgrade to 3.3 one day ;-))

Seb.


On 15/01/14 09:39, Ian Stuart wrote:
> I'm creating new data objects in an EPrints repository (EP3.2 as it
> happens) to support a new service within my repo.
> The idea is that a "subscriber" can register to receive a number of
> "postcards", where each postcard is a list of citations of new records
> in a [list of] department[s], emailed to a specified email address.
>
> I have two Objects: a "Subscriber" and a "Postcard", based very heavily
> on the "EPrint" and "Document" Data Objects.
>
> The fundamental code for the two objects is listed at the end of the email.
>
> The full code is syntactically correct, and loads into EPrints.
>
> When I use the code, I start with a user_id, and want to get the list of
> postcards associated with that user, so I have code thus:
>
>     # Before we do anything - we need to get the subscriber object
>     my $subs_ds = $session->get_repository->get_dataset("subscriber");
>     my $subscriber;
>
>     { # Localise this search
>       my $searchexp = EPrints::Search->new(
>         session     => $session,
>         dataset     => $subs_ds,
>       );
>       $searchexp->add_field( $subs_ds->get_field("userid"), $user_id );
>       warn $searchexp->render_description->toString;
>       my $results = $searchexp->perform_search;
>
>       if ($results->count) {
>         my @records = $searchexp->perform_search->slice(0,1); # Get
> records from position 0, for a count of 1 records
>         $subscriber = $records[0]
>       } else {
>         $subscriber = EPrints::DataObj::Subscriber->create( $session,
> {userid => $user_id }, $subs_ds );
>       }
>     }
>
>     # Having got a subscriber object, lets get a list of postcards they have
>     # Postcards are 1 email address and some number of repositories
>     warn "got subscriber " . $subscriber->get_id . "\n";
>     my $postcards = $subscriber->get_value( 'postcards' );
>
> This code successfully returns a matching "Subscriber", however the
> final line in that code is causing me problems... I get the error
>
>     dataset postcard has no field: datasetid
>
> I have double-checked my code against that of EPrints::DataObj::EPrint
> and EPrints::DataObj::Document - neither of them have a datasetid field,
> and my own objects are creating records in exactly the same way!
>
> I've a few questions... but mostly I'd like someone to try to explain
> how new data-objects should be made, and what's needed.
>
> Oh - and once I've got this working, I *WILL* add documentation to the
> Wiki... if nothing else, it'll help me understand what my codes doing,
> and why :chuckle:
>
>
>
>
> package EPrints::DataObj::Subscriber;
>
> our @ISA = ('EPrints::DataObj');
>
> use EPrints;
>
> sub get_system_field_info {
>     my ($class) = @_;
>
> return (
>       { name => "subscriberid", type => "counter",
>         required => 1, import => 0, can_clone => 0,
>         sql_counter => "subscriberid"
>       },
>       { name => "userid", type => "text", required => 1 },
>       { name => "postcards", type => "subobject",
>         datasetid => 'postcard', multiple  => 1
>       },
>     );
> } ## end sub get_system_field_info
>
> sub get_dataset_id {
>     return "subscriber";
> }
>
> sub get_all_postcards {
>     my ($self) = @_;
>
>     return @{ ( $self->get_value("postcards") ) } ;
>    } ## end sub get_all_postcards
>
> 1;
> package EPrints::DataObj::Postcard;
>
> our @ISA = ('EPrints::DataObj::SubObject');
>
> use EPrints;
>
> sub get_system_field_info {
>     my ($class) = @_;
>
>     return (
>       { name => "cardid", type => "counter",
>         required => 1, import => 0, show_in_html => 0,
>         can_clone => 0, sql_counter  => "postcardid"
>       },
>       { name => "email", type => "text", required => 1 },
>       { name => "subscriberid", type => "itemref",
>         datasetid => "subscriber", required => 1, show_in_html => 0
>       },
>       { name => "repos", type => "compound", multiple => 1,
>         fields => [
>           { sub_name => "repoid",   type => "text", },
>           { sub_name => "reponame", type => "text", },
>         ],
>       },
>     );
>
> } ## end sub get_system_field_info
>
> sub get_dataset_id {
>     return "postcard";
> }
>
> sub get_parent {
>     my ( $self, $datasetid, $objectid ) = @_;
>
>     $datasetid = "subscriber";
>     $objectid  = $self->get_value("subscriberid");
>
>     return $self->SUPER::get_parent( $datasetid, $objectid );
> } ## end sub get_parent
> 1;
>
>