[Deprecated] DMZ 1.5.3 (DataMapper OverZealous Edition)

[eluser]OverZealous[/eluser]
@warrennz
There is no way to save more than one relationship between the same ids using the same relationship name. This is mentioned in the notes on the first post. (The id field is not actually used internally by DataMapper. It is simply recommended for good database design.)

If you want to save what you are showing, you'll need to specify the relationships more accurately. For example, if you are trying to save creator, editor, and assigned_to, all which point to a User, then you need to create multiple relationships, one for each type. As long as you are not creating a self-relationship, then these can all be stored in the same table (e.g.: posts_users), which will need to have a column for each type (e.g.: post_id, creator_id, editor_id, assigned_to_id), all of which need to allow NULLs. Alternatively, you can store the $has_one relationships on the posts table.

In other words, what are you trying to store there?

There is no way in your example for DM to ever know which row you want to save into. In fact, there is simply no way to even create multiple rows between the same two objects, as DM uses the two ids to perform lookups.

One possible way around it, in your example, is to have a dedicated intermediate model to manage the relationships. For example, you could have a model called MachinePart, and it would look like this:

Code:

// ------------------------------
// model
// ------------------------------
class MachinePart extends DataMapper {
    $has_one = array('machine', 'part');
    // etc.
}

// ------------------------------
// table:
// ------------------------------
machineparts: id, machine_id, part_id, setting_1, setting_2, ...

// ------------------------------
// controller:
// ------------------------------
// add a part
$m = new Machine(); ...
$p = new Part(); ...
$mp = new MachinePart();
$mp->setting_1 = $setting_1_value;
$mp->save(array($m, $p));

// get all parts for the machine $m
$parts = new Part();
// simple trick to avoid making multiple queries
$parts->where_related_machinepart('machine_id', $m->id);
$parts->join_related('machinepart', array('setting_1', 'setting_2', ...));
$parts->get();
foreach($parts->all as $part) {
    echo($part->name);
    echo($part->machinepart_setting_1);
    echo($part->machinepart_setting_2);
    ...
}

// remove all machine-part relationships
$m->machinepart->get()->delete_all();

// remove a specific machine-part relationship, by id
$mp = new MachinePart();
$mp->get_by_id($mp_id);
$mp->delete(); // also removes relationships

Does that make sense?

@abbie
warrennz is correct, in that you use set_join_field, which is explained in the first post, under the heading Update, View, and Query Extra Columns on Join Tables.