DBIx:Class many-to-many relationship with additional attribute - perl

Question

I'm working with DBIx::Class in Catalyst framework. My local goal is to add a new many-to-many relationship between users and, let's say, tasks. But there's one little trick I need. User can have different roles in task (like 'worker' or 'spectator').
So I have users table with these fields:
id
name
I have task table with these fields:
id
title
description
And I have relationship table user_tasks with these fields:
user_id
task_id
role
I have set up has_many from users to user_tasks, has_many from tasks to user_tasks and corresponding many_to_many relationships between users and tasks. And that plain part works as it should.
Then, for example, I want to get my user list including user's role in task identified by $task_id:
my $users = $schema->resultset('User')->with_task_role($task_id);
while (my $u = $users->next) {
print "User: " . $u->name . ", role: " . $u->get_column('task_role');
}
So how should I code this with_task_role custom resultset to get this additional field with user's task role in my query?

Answer 1

First of all many-to-many is not a relationship. It's a accessor (a relationship bridge).
Second, the DBIx::Class has an excellent documentation. Take a look at join/prefetch.
In your ResultSet/User.pm file you should have something like:
sub with_task_role {
my ($self, $task_id) = #_;
return $self->search({
'task.task_id' => $task_id,
},
{
join => { 'user_task' => 'task' },
prefetch => { 'user_task' => 'task' },
},
);
}
PS: Sorry, I didn't see that Ashley already answered
PS2: Before the last line "})" should be ")" only (fixed it)

Answer 2

This is some User resultset code, unchanged, from the XUL (which is
no longer supported by any browsers) slideshow of the DBIC
master class (.xul resource). I highly recommend downloading the slides, which read fine as plain text, to review. They were a great eye-opener for resultsets for me.
You'll have to adjust the result source names to match your own but
this should be what you want and a bit more flexible to boot with the
_role_to_id which allows you to pass role objects or ids.
sub with_role {
my ($self, $role) = #_;
$self->search({
'role_links.role_id' => $role->id
},
{ join => 'role_links' }
);
}
sub _role_to_id {
my ($self, $role) = #_;
return blessed($role) ? $role->id : $role;
}
sub with_any_role {
my ($self, #roles) = #_;
$self->search({
'role_links.role_id' => {
-in => [
map { $self->_role_to_id($_) } #roles
]
}
},
{ join => 'role_links' }
);
}