Can't store tags with question: string given

Question

I want to store tags with question in my project, and the relation between question and tags is many to many polymorphic (poly because I have another tables and they have tags field too)

In my QuestionController(), when I want to store a question and tags, I get this error:

Argument 1 passed to Illuminate\Database\Eloquent\Relations\BelongsToMany::save() must be an instance of Illuminate\Database\Eloquent\Model, string given

When I use save instead of saveMany() gives this error:

"message": "Argument 1 passed to Illuminate\Database\Eloquent\Relations\BelongsToMany::save() must be an instance of Illuminate\Database\Eloquent\Model, array given

I also used sync(), but tags aren't stored in the database.

I tasted it with postman.

And the method is this:

 public function store(StoreQuestionRequest $request)
    {
        $validatedData = $request->all();

      ////Because there is no need storage images and question codes

        $question = Question::create($validatedData); //store question

        //store tags
        $tag = new Tag();

        $tags = explode(",", $request->tag);//separate tags

        $tag['tag'] = $tags;

        $question->tags()->saveMany($tags);

        return response()->json([
            'success'=>true,
            'message'=> 'successfully',
            'data'=>$question
        ]);
    }

So if you need to know about relations, these are my models:

Question:

 public function tags(){
        return $this->morphToMany(Tag::class, 'taggable');
    }

Tag:

 public function questions(){
        return $this->morphedByMany(Question::class, 'taggable');
    }

Answer 1

it solved :

 public function store(StoreQuestionRequest $request)
    {
        $validatedData = $request->all();

      ////Because there is no need storage images and question codes

        $question = Question::create($validatedData); //store question

        //store tags

       $tagNames = explode(",", $request->tag);//separate tags

        $tagIds = [];

        foreach($tagNames as $tagName)
        {
            $tag = Tag::firstOrCreate(['tag'=>$tagName]);
            if($tag)
            {
              $tagIds[] = $tag->id;
            }
        }
        $question->tags()->sync($tagIds);


        return response()->json([
            'success'=>true,
            'message'=> 'successfully',
            'data'=>$question
        ]);
    }