Verify belongsToMany for update function in controller laravel 5.4 - laravel

Question

I'm creating this sort of database with some movies information.
The logic structure is pretty simple one movie has many actors and one actor have done many movies so it's a many to many relationship.
I'm also using select2 library to have a simple input where write actors like tags, separating them with commas or spacebar (here the link to docs) and below a simple snapshot to better understand the result
In the create/store function I don't need to check if any relation exists yet because the movie it's new. So I just need to check if actors already exists in the database, if not save them.
My controller store() function looks like:
foreach ($request->input('actors') as $key => $new_actor) {
// if actors doesn't exist in the db it save it.
$check = Actor::where('name', '=', $new_actor)->count();
if ($check === 0) {
$actor = new Actor;
$actor->name = $new_actor;
$actor->save();
}
// Here it creates the relationship
$actor = Actor::where('name', '=', $new_actor)->first();
$film->actors()->attach($actor->id);
}
The problem
when I edit a movie changing the actors, for example deleting or adding a new actor. I need to check in the controller if there are new relationship or if I have to delete some. How can I do it?
This is my controller update() function and of course doesn't work at all
foreach ($request->input('actors') as $key => $new_actor) {
// if actors doesn't exist in the db it save it.
$check = Actor::where('name', '=', $new_actor)->count();
if ($check === 0) {
$actor = new Actor;
$actor->name = $new_actor;
$actor->save();
}
$actors = $film->actors()->get();
foreach ($actors as $key => $actor) {
if ($actor->name === $new_actor) {
$actor = Actor::where('name', '=', $new_actor)->first();
$film->actors()->attach($actor->id);
}
}
}
Thanks for your help.

Answer 1

There is not direct way to do this with using the eloquent it. But you can do with the using db facade like this
$actors_film_relation = \DB::table('actor_film')->pluck('actor_id')->unique();
By using this now you can get the list of the actors that are attached with atleast one film.
Before deleting user you can check that actor_id is not inside the $actor_film_relation list like this
if( !in_array( $id, $actors_film_realtion)) { $actor->delete(); }
So now, the actor that is related to atleast one film will be not deleted.

Answer 2

Ok I found my way. With the first part checks if there are new actors and if true, it creates a new row in the actors table. With the second part, check if there are changes from the input comparing the new array with the relationship saved in the db, so it can detect if some actors were deleted and then deletes the relationship too.
foreach ($request->input('actors') as $key => $new_actor) {
// if actors doesn't exist in the db it save it.
$check = Actor::where('name', '=', $new_actor)->count();
if ($check === 0) {
$actor = new Actor;
$actor->name = $new_actor;
$actor->save();
}
// If the relation doesn't exists it creates it.
if (!$film->hasActor($new_actor)) {
$actor = Actor::where('name', '=', $new_actor)->first();
$film->actors()->attach($actor->id);
}
// If the relation has been deleted, it deletes it.
$actors = $film->actors()->get();
$new_actors = $request->input('actors');
foreach ($actors as $key => $actor) {
$check = in_array($actor->name, $new_actors);
if ($check === false) {
$film->actors()->detach($actor->id);
}
}
}