Laravel在Eloquent mutators中保存了多对多的关系

我有两个具有多对多关系的模型.我希望能够使用一组id设置一个特定的属性,并在mutator中建立关系,如下所示:

tags()->get([ 'tag_id' ]);

        foreach ($tags as $tag) {
            $tag_ids[] = $tag->tag_id;
        }

        return $tag_ids;
    }

    public function setTagsAttribute($tag_ids)
    {
        foreach ($tag_ids as $tag_id) {
            $this->tags()->attach($tag_id);
        }
    }

    public function tags()
    {
        return $this->belongsToMany('Tag');
    }

}

profiles()->get([ 'profile_id' ]);

        foreach ($profiles as $profile) {
            $profile_ids[] = $profile->profile_id;
        }

        return $profile_ids;
    }

    public function profiles()
    {
        return $this->belongsToMany('Profile');
    }

}

但是该setTagsAttribute功能未按预期工作.我收到以下错误:SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'profile_id' cannot be null (SQL: insert intoprofile_tag (profile_id ,tag_id) values (?, ?)) (Bindings: array ( 0 => NULL, 1 => 1, ))