Laravel 5.3 withCount() nested relation

问题

The model structure is as follows

Tutorial -> (hasMany) Chapters -> (hasMany) videos

How can we load number of videos (video_count) from Tutorial Model with laravel 5.3's withCount() method

I have tried:

Tutorial::withCount('chapters')
->withCount('chapters.videos') // this gives error: Call to undefined method Illuminate\Database\Query\Builder::chapters.videos()
->all();

Edit

This works, Any Better solution?

Tutorial::withCount('chapters')
->with(['chapters' => function($query){
    $query->withCount('videos');
}])
->all();

回答1:

You can only do a withCount() on a defined relation of the model.

However, a relationship can be hasManyThrough which would achieve what you are after.

class Tutorial extends Model
{
    function chapters()
    {
        return $this->hasMany('App\Chapter');
    }

    function videos()
    {
        return $this->hasManyThrough('App\Video', 'App\Chapter');
    }
}

And then you can do:

Tutorial::withCount(['chapters', 'videos'])

Docs:

• https://laravel.com/docs/5.3/eloquent-relationships#has-many-through

来源：https://stackoverflow.com/questions/39633691/laravel-5-3-withcount-nested-relation