Create new entry (One to One Polymorphic relationship) - laravel

Question

Premise
I am creating a small app with User profiles that can host a list of items of different types.
Each Item can be a Link, Card, Video. So each layout can be optimized accordingly. A bit like Tumblr, if you like.
The setup
For this reason, I've opted to use a one-to-one a polymorphic relationship (maybe overkill?), with an items table that has additional columns like position (so that a user can reorder the items).
The items table:
id
user_id (foreign key)
itemable_id
itemable_type
position
...
My models look like:
Item model
public function itemable()
{
return $this->morphTo();
}
public function user()
...
Link model
public function item()
{
return $this->morphOne('\App\Item', 'itemable');
}
public function user()
...
Card model
public function item()
{
return $this->morphOne('\App\Item', 'itemable');
}
public function user()
...
…and so on for the other Item types.
Finally, in ItemController, I'm creating a dummy Link for debug purposes:
// ...
$newLink = new Link();
$newLink->url = 'example.org';
$newLink->title = 'Example Website NEW';
$newLink->user_id = $user->id;
$user->items()->save($newLink);
// ...
But, unlike how I expected, the new entry in the items table doesn't get created. I have to that myself instead, manually once I've stored the $newLink Link.
The question
Is this normal? I would have expected to have Link (with itemable_id and itemable_type created automatically.
If so, I'm definitely missing something here. How can I make Laravel create the items entry automatically?

Answer 1

use associate so it will be like below:
$user->items()->associate($newLink);