本文介绍了Laravel 5.3 withCount() 嵌套关系的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
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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