On 1/9/06, Scott Karns <[EMAIL PROTECTED]> wrote:
> OK, that certainly works. Perhaps not exactly as I had expected, but it works.
> I guess I was approaching it as though the query was a multi-table inner join
> with the iterator returning a single row of the query result containing all
> columns of all tables involved.
That's not very useful if you want to iterate over all
School::CourseSection objects but *don't* necessarily want to iterate
over all sub-objects. If it was done the way you describe, you'd be
required to manually iterate over every single sub-object even if you
weren't interested in all of those sub-objects for each "main"
(School::CourseSection) object.
> I guess I need to look at approaching the listing of instructors and the
> classes they teach from a different angle, as sorting that list by instructor
> name should be possible (and easy!)
If you want a list of "instructors and the classes they teach, sorted
by instructor name" with your current table structure, then try
something like this:
package School::Person;
use School::ClassInstructor;
...
# Add a relationship between a person and
School::Person->meta->relationships
(
course_sections =>
{
type => 'many to many',
map_class => 'School::ClassInstructor',
# Note that these are probably optional since the
# class_instructor table has just two well-defined
# foreign keys, so it's obvious what maps to what.
map_from => 'instructor',
map_to => 'the_class',
},
);
package School::Person::Manager;
use strict;
use School::Person; # don't forget to use() the object_class!
use base 'Rose::DB::Object::Manager';
sub object_class { 'School::Person' }
__PACKAGE__->make_manager_methods('persons');
Now the loop:
$iterator =
School::Person::Manager->get_persons_iterator(
require_objects => [ 'course_sections.course',
'course_sections.room' ],
sort_by => [ qw(lname fname) ]);
while(my $instructor = $iterator ->next)
{
foreach my $cs ($instructor->course_sections)
{
print $instructor->fname, ' ', $instructor->lname,
' teaches ', $cs->course->short_cname,
', section ', $cs->sect_num,
' in ', $cs->room->short_rmname, ".\n";
}
}
Note that the sort_by arguments no longer have to be qualified since
the "person" table to which they belong is now the primary table.
Also note that you could remove all of the "require_objects" args in
the get_persons_iterator() call and leave the loop code as-is. The
difference would be that many more queries would be run, of course.
With the require_objects arguments as shown, all information should be
retrieved in a single query. But semantically, that's an optimization
from the perspective of the loop code.
-John
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