Can't save data in hook_node_update()

Question

I have a node type with two field_collection fields. When I save the node I need to write the entity_id of the first field_collection into the secondo field_collection. This is my code:

function mymodule_node_update($node){
    $entity_id = $node->field_collection_1['und'][0]['value'];
    $entiry_array = entity_load('field_collection_item',array(entity_id));
    $entity = array_shift($entity_array);

    if (empty($entity->field_reference['und'][0]['value'])) {
        $entity->field_reference['und'][0]['value'] = $node->field_collection_2['und'][0]['value'];
        $entity->save();
    }
}

There are 2 problems there: 1) in hook_node_update() data is not committed yet https://drupal.org/node/1677830 2) $entity->save() triggers again hook_node_update() (and in my opinion it shouldn't)

So at the end in $node->field_collection_1 I have the right id $node->field_collection_2 would have, but due to recursive call to hook_node_update() and the fact that in hook_node_update() data is not committed to database yet field_collection_2 entity and all changes made to the node vanish.

Can someone suggest me a possible solution?

Thank you

Answer 1

hook_node_presave($node)

Act on a node being inserted or updated.

This hook is invoked from node_save() before the node is saved to the database. Parameters

$node: The node that is being inserted or updated.

function hook_node_presave($node) {

if ($node->type == 'your_node_type') {
// you can write your desired code here


}

}

Answer 2

If you want to guarantee that everything including access rights is written to the database, you can register a shutdown function in one of the node hooks. You do that with drupal_register_shutdown_function passing in an arbitrary function name and the arguments. Here's how it might look for your case in hook_node_update:

function mymodule_node_update($node) {
  // only register shutdown for node of the right type
  // let's assume the node content type is 'foobar'
  if ($node->type == 'foobar') {
    drupal_register_shutdown_function('node_voodoo_on_shutdown', $node);
  }
}

function node_voodoo_on_shutdown($node) {
    $entity_id = $node->field_collection_1['und'][0]['value'];
    $entity = entity_load_single('field_collection_item',entity_id);

    if (empty($entity->field_reference['und'][0]['value'])) {
        $entity->field_reference['und'][0]['value'] = $node->field_collection_2['und'][0]['value'];
        $entity->save();
    }
}