DMZ 1.7.1 (DataMapper OverZealous Edition)

[eluser]j0nxiest[/eluser]
I didn't quite get from the documentation how to work with related items with the from_array method. I tried to do like this:

The form:

Code:

<?php
$usergroup = new Usergroup();
$usergroup->where('group_name','user')->get();
?>
<label for="username">Username: &lt;input type="text" name="username" id="username" class="text" value="&lt;?=set_value('username', $user-&gt;username); ?&gt;" /></label><br/>
&lt;input type="hidden" name="usergroup" value="&lt;?=set_value('usergroup', $usergroup-&gt;id)?&gt;" />

The handler:

Code:

$user = new User();
$user->from_array($_POST);
$user->save();

But it complaints that the usergroup relation is not set, what am i doing wrong? The usergroup var is POSTed correctly.