调用关联的eloquent模型的类方法

Question

I'm having trouble figuring out how to call a class function, in this case File->saveFile() through the parent class Article

class Article extends Model {
  public $table = 'pl_gen_article';

  public function background_image () {
    return $this->morphOne('App\Ubercms\File', 'fileable');
  }
}

class File extends Model {
  public $table = 'ubercms_file';

  public function saveFile (UploadedFile $file) {}
}


$articleId = \Route::input('id');
$article = Article::findOrFail($articleId);
$file = $request->file('image');

// ----------------------
// Attempts

// 1.
$article->background_image->saveFile($file)

// 2.
$image = new $article->background_image();
$image->saveFile($file);

How do I create a File model instance from Article model?

Answer 1

Through the Laravel Api Docs traced the response of $article->background_image() which as MorphOne instance, where I can call firstOrNew which returns an File instance and I'm able to call saveFile afterwards.

$model = $article->background_image()->firstOrNew([]);
$model->saveFile($file);