このようなものが必要です
public function reviewRows()
{
return $this->hasManyThrough('ReviewRow', 'Review');
}
public function avgRating()
{
return $this->reviewRows()
->selectRaw('avg(rating) as aggregate, product_id')
->groupBy('product_id');
}
public function getAvgRatingAttribute()
{
if ( ! array_key_exists('avgRating', $this->relations)) {
$this->load('avgRating');
}
$relation = $this->getRelation('avgRating')->first();
return ($relation) ? $relation->aggregate : null;
}
次に、これと同じくらい簡単です:
// eager loading
$products = Product::with('avgRating')->get();
$products->first()->avgRating; // '82.200' | null
// lazy loading via dynamic property
$product = Product::first()
$product->avgRating; // '82.200' | null