Laravel 5.3 withCount() 嵌套关系

问题描述

模型结构如下

教程 -> (hasMany) 章节 -> (hasMany) 视频

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

我们如何使用 laravel 5.3 的 withCount() 方法从教程模型加载视频数量(video_count)

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

我试过了:

Tutorial::withCount('chapters')
->withCount('chapters.videos') // this gives error: Call to undefined method IlluminateDatabaseQueryBuilder::chapters.videos()
->all();

编辑

这行得通，还有更好的解决方案吗?

This works, Any Better solution?

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

推荐答案

您只能对模型的定义关系执行 withCount().

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

但是，关系可以是 hasManyThrough，这将实现您的目标.

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

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

    function videos()
    {
        return $this->hasManyThrough('AppVideo', 'AppChapter');
    }
}

然后你可以这样做:

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

文档:

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

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