I'm looking for a solution to my problem that is pretty simple in fact. 
I'm on an importing task in which I have to create programmatically a node and then populate all its fields. 

As we're using the [Scald][1] module, we can add several medias to a node. But I can't figure out how to associate several medias to a node ? 

I tried the following : 

 foreach ($file_atoms as $i => $atom) {
 $node_wrapper->field_atom[$i] = $atom->sid;
 }

or : 

 foreach ($file_atoms as $i => $atom) {
 $node_wrapper->field_atom[$i]->set($atom->sid);
 }

But I get the following error : 
 
>Error: Cannot use object of type EntityDrupalWrapper as array

I followed the doc on [this page][2] but it does not seems to work.. 

Can somebody help me ? 

I'm encountering the same problem with taxonomies : I'm not able to set multiple values to the node wrapper.


 [1]: https://www.drupal.org/project/scald
 [2]: https://www.drupal.org/documentation/entity-metadata-wrappers