Laravel relationship one to one doesnt work with single page view - laravel

Question

I have created two models called video and file using Laravel 6.
A video can have only one file.
This is the relationship I created:
Video
public function file() {
return $this->hasOne('App\File');
}
File model
public function video() {
return $this->hasOne('App\Video');
}
If I loop all videos then I get the related media
#foreach($videos as $video)
{{$video->link->media}}
#endforeach
If I go to the related video single page it doesnt work.
{{$video->link->media}
Here the route:
Route::get('/video/{slug}', 'HomeController#singleVideo')->name('single');
I get following error:
Trying to get property 'media' of non-object
I also add the table Schema:
Schema::create('files', function (Blueprint $table) {
$table->bigIncrements('id');
$table->string('media')->default('none');
$table->unsignedBigInteger('video_id');
$table->timestamps();
});
Schema::create('videos', function (Blueprint $table) {
$table->bigIncrements('id');
$table->string('title',128);
$table->string('slug')->unique();
$table->text('description');
$table->string('url',247);
$table->string('category',128);
$table->unsignedBigInteger('views')->default(200);
$table->string('video_youtube_status')->default('off');
$table->string('video_status')->default('off');
$table->string('status')->default('off');
$table->timestamps();
});
Model Video
protected $guarded = [];
public function file() {
return $this->hasOne('App\File');
}
....

Answer 1

According to the Laravel documentation, the relation "hasOne" is not applied in this way, the primary model(let's say it's File) will have hasOne like in your code, but the secondary Model will have the Inverse Of The Relationship, which is 'belongsTo' so, in your video Model you should write:
public function file() {
return $this->belongsTo('App\File','file_id');
}
This will allows you to access to the entities like:
$video->file->some_property
$file->video->another_property
and another major problem in your videos table:
this table must have a foreign key to files table, which means:
in your videos migration you should add :
$table->unsignedBigInteger('file_id')->nullable(false);
$table->foreign('file_id')->references('id')->on('files');

Answer 2

According to Laravel documentation
You should implement the use of belognsTo relationship
and your query to get your results set must include the use of method with()
$users = User::with('podcasts')->get();
foreach ($users->flatMap->podcasts as $podcast) {
echo $podcast->subscription->created_at;
}