Custom method not work on HasMany relation - laravel

Question

I trying to call a custom method from a model by relation.
User Model:
class User extends Model
{
public function files()
{
return $this->hasMany(Files::class, 'file_id', 'id');
}
}
File Model:
class Files extends Model
{
public function cover()
{
dd('blah blah');
}
}
In my controller I said:
$user = User::find(1);
$user->files()->cover();
But I will get this error:
Call to undefined method Illuminate\Database\Eloquent\Relations\HasMany::cover()
What is the problem in my code?

Answer 1

Basically you are calling your cover() method over the collection. That's why that is not working.
You are using hasMany Laravel relationship. And this hasMany returns collection of related records(items). And yo can't call any model function on that directly.
But if you wan to call function on this. you need to firstly loop the items, like below example:-
$user = User::find(1);
foreach($user->files() as $file) {
$file->cover();
}
Above code will provide you output. Try this.

Answer 2

If you want to get all the covers of you files, you can do this :
$user = User::with('files.cover')->find(1);
$covers = $user->files->pluck('cover')->flatten();
I want to use this method to check and then store the cover. because I need to check the cover before insert I couldn't use create method, it will be an alias to create. so I couldn't overwrite to create method?
From this, you can do the following:
foreach($user->files as $file){
$cover = $file->cover()->firstOrCreate(['attribute' => $value]);
// If you want to check if you just created the cover
if($cover->wasRecentlyCreated){
// Do stuff
}
}