UR::Object::Iterator - API for iterating through objects matching a rule

UR documentation Contained in the UR distribution.

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NAME

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UR::Object::Iterator - API for iterating through objects matching a rule

SYNOPSIS

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  my $rule = UR::BoolExpr->resolve('Some::Class', foo => 1);
  my $iter = UR::Object::Iterator->create_for_filter_rule($rule);
  while (my $obj = $iter->next()) {
      print "Got an object: ",$obj->id,"\n";
  }

  # Equivalent
  my $iter2 = Some::Class->create_iterator(foo => 1);
  while (my $obj = $iter2->next()) {
      print "Got an object: ",$obj->id,"\n";
  }

DESCRIPTION

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get(), implemented in UR::Object, is the usual way for retrieving sets of objects matching particular properties. When the result set of data is large, it is often more efficient to use an iterator to access the data instead of getting it all in one list.

UR::Object implements create_iterator(), which is just a wrapper around create_for_filter_rule().

UR::Object::Iterator instances are normal Perl object references, not UR-based objects. They do not live in the Context's object cache, and obey the normal Perl rules about scoping.

METHODS

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create_for_filter_rule
  $iter = UR::Object::Iterator->create_for_filter_rule($boolexpr);

Creates an iterator object based on the given BoolExpr (rule). Under the hood, it calls get_objects_for_class_and_rule() on the current Context with the $return_closure flag set to true.

next
  $obj = $iter->next();

Return the next object matching the iterator's rule. When there are no more matching objects, it returns undef.

SEE ALSO

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UR::Object, UR::Context

UR documentation Contained in the UR distribution. 
package UR::Object::Iterator;

use strict;
use warnings;

# These are no longer UR Objects.  They're regular blessed references that
# get garbage collected in the regular ways

#use UR;
#
#UR::Object::Type->define(
#    class_name      => __PACKAGE__,
#    has => [
#        filter_rule_id          => {},
#    ],
#);
#
#sub create_for_filter_rule {
#    my $class = shift;
#    my $filter_rule = shift;
#    my $code = $UR::Context::current->get_objects_for_class_and_rule($filter_rule->subject_class_name,$filter_rule,undef,1);
#    
#    my $self = $class->SUPER::create(
#        # TODO: some bug with frozen items?
#        filter_rule_id      => $filter_rule->id,        
#    );
#    
#    $self->_iteration_closure($code);    
#    return $self;
#}

sub create {
    die "Don't call UR::Object::Iterator->create(), use create_for_filter_rule() instead";
}

sub create_for_filter_rule {
    my $class = shift;
    my $filter_rule = shift;
   

    my $code = $UR::Context::current->get_objects_for_class_and_rule($filter_rule->subject_class_name,$filter_rule,undef,1);
    
    my $self = bless { filter_rule_id => $filter_rule->id,
                       _iteration_closure => $code},
               __PACKAGE__;
    return $self;
}


sub _iteration_closure {
    my $self = shift;
    if (@_) {
        return $self->{_iteration_closure} = shift;
    }
    $self->{_iteration_closure};
}


sub next {
    shift->{_iteration_closure}->(@_);
}


1;