Create relationships in hashtags - laravel

Question

I want to create a hashtags system. Currently I have this code:
private function hashtags($post){
$htag = '#';
$arr = explode(" ", $post->description);
$arrc = count($arr);
$i = 0;
while($i < $arrc){
if(substr($arr[$i], 0, 1) === $htag ){
$hash = Hashtag::where('name', ltrim($arr[$i], '#'))
->where('slug', str_slug(ltrim($arr[$i], '#')))
->first();
if(!$hash){
Hashtag::create([
'name' => ltrim($arr[$i], '#'),
'type' => 1,
'slug' => str_slug(ltrim($arr[$i], '#'))
]);
}
$current_hash = Hashtag::where('type', 1)
->where('name', ltrim($arr[$i], '#'))
->first();
\DB::insert('insert into hashtag_post (hashtag_id, post_id) values (' .$current_hash->id. ', ' .$post->id. ')');
}
$i++;
}
}
This code isn't good for me because I prefer use attach method but if I try use $post->hashtags()->attach([1, 2, 3]); or other array which I created with hashtag's id, it display error:
"Call to undefined method App\Post::hashtags()".
My question is:How I can use attach with this example and how I can improve my code. It doesn't look well.

Answer 1

Firstly, your relationships should be public methods.
Secondly, both relationships should be belongsToMany.
Post class
public function hashtags()
{
return $this->belongsToMany(Hashtag::class);
}
Hashtag class
public function posts()
{
return $this->belongsToMany(Post::class);
}
Just an FYI, Laravel comes with helper methods that can reduce how much you have to write e.g. firstOrCreate(). So, this:
$hash = Hashtag::where('name', ltrim($arr[$i], '#'))
->where('slug', str_slug(ltrim($arr[$i], '#')))
->first();
if(!$hash){
Hashtag::create([
'name' => ltrim($arr[$i], '#'),
'type' => 1,
'slug' => str_slug(ltrim($arr[$i], '#'))
]);
}
can become:
$hash = Hash::firstOrCreate(
['name' => ltrim($arr[$i], '#'), 'slug' => str_slug(ltrim($arr[$i], '#'))],
['type' => 1]
);