Entity metadata wrapper - php

Question

i'm getting error with metadata wrapper.
i have a field test => entity reference multiple which is a selection list.I get the following Error EntityMetadataWrapperException : Invalid data value given. Be sure it matches the required data type and format.
$account = entity_load_single('user', $user->uid);
$acc_wrapper = entity_metadata_wrapper('user', $account);
$list = $acc_wrapper->test->value();
$exists = FALSE;
if (!empty($list)) {
foreach ($list as $item) {
if ($item->nid == $form_state['storage']['node']->nid) {
$exists = TRUE;
break;
}
}
}
if (!$exists) {
if (!$list) {
$list = array();
$list[] = $form_state['storage']['node']->nid;
}
$acc_wrapper->test->set($list);
$acc_wrapper->save();

Answer 1

1rst quick tips
$account = entity_load_single('user', $user->uid);
$acc_wrapper = entity_metadata_wrapper('user', $account);
You don't need to load the entity unless you need it loaded after (Or it's already loaded). All you need is the id, and let entity_metadata_wrapper magic operate.
$acc_wrapper = entity_metadata_wrapper('user', $user->uid);
I think your error is here
if (!$list) {
$list = array();
$list[] = $form_state['storage']['node']->nid;
}
$list is always initiated because of "$list = $acc_wrapper->test->value();", so you never fullfill the condition, and then you are trying to set it back and save it (because you are missing a '}' )... Makes no sense...
Could try this version ?
$acc_wrapper = entity_metadata_wrapper('user', $user->uid);
$list = $acc_wrapper->test->value();
$exists = FALSE;
if (!empty($list)) {
foreach ($list as $item) {
if ($item->nid == $form_state['storage']['node']->nid) {
$exists = TRUE;
break;
}
}
}
if (!$exists && !$list) {
$list = array($form_state['storage']['node']->nid);
$acc_wrapper->test = $list;
$acc_wrapper->save();
}