I have two tables:

images
-id
-name
-imageable_id
-imageable_type

article
-id
-title
....
-image_id

I've created a images function to get all images that returns this relationship:

public function images()
{
    return $this->morphMany('App\Image', 'imageable');
}

and that works great, but I also want to have a mainImage function that will use image_id on article to get the image with that id from the image table. I've tried

hasOne('App\Image', 'id', 'image_id')

With this code

$imageId = $request->input('mainImage');
if(!empty($imageId)){
    $image = Image::find($imageId);
    $listing->mainImage()->save($image);
}

And that doesn't seem to set image_id to anything but null. Thank you in advance for any help!