为什么数据透视表上的相关行不会被多态删除多少？

Question

Tables associated with the models Post, Tag, Taggable are in polymorphic relationship. If I delete a tag then still its tag_id may have been used on taggables table. Do I have to delete all of its associations manually ?

And what is the role of following code on Taggable model? The code seems to work without it.

public function taggables() {
    return $this->morphTo();
}

Answer 1

The code on Taggable model is called a relationship, basically when you want to retrieve all taggables => $taggable->taggable will return all results in taggables table.

To be able to delete polymorphic relationship you need to use detach from your parent classes, which in this case are Post and Video => $post->tags()->detach($tagId) or $video->tags()->detach($tagId)

To add a polymorphic relationship you can use attach => $post->tags()->attach($tagId) or $video->tags()->attach($tagId)

Both functions also can take other parameters, and you can check them out on their official docs