Laravel得到了最后一篇文章的主题

Question

I'm trying to do that , get list of topics order by who has new post so I create a relation in topic model like that

public function latest_post()
{
    return $this->hasOne(Post::class)->latest();
}

then I used the query like that

Topic::where('locale',$this->locale)->with('latest_post')->paginate(15)->sortByDesc('latest_post.created_at');

but it's giving me an error

Collection::render does not exist

so I change the sort to orderBy like that

Topic::where('locale',$this->locale)->with('latest_post')->orderBy('latest_post','DESC')->paginate(15);

but this also gives me another error

Unknown column 'latest_post' in 'order clause'

how can solve this issue?

Answer 1

Hmmm. Try this

$topic = Post::orderBy('created_at','desc')->first()->join('topics', 'topics.id', '=', 'posts.topic_id')->first();

Or in your post model:

    public function Topic()
    {
        return $this->belongsTo(Topic::class, 'topic_id');
    }

To get the last active topic:

$topic = Post::orderBy('created_at','desc')->first()->Topic;