Rails-对同一记录的多个属性进行操作

Question

Given a Review model and a reviews table defined as follow:

 id | avg_rating | reviews_count
---------------------------------
  1 |          4 |            12
  2 |          5 |             2
  3 |          1 |             9
  4 |          3 |             1

I need to calculate a weighted_rating; currently I do:

sum = 0

Review.all.each do |review|
  sum = sum + review.avg_rating * review.reviews_count
end

weighted_rating = sum / Review.sum(:reviews_count)

Is there a cooler & functional way to get this done in Rails?

Answer 1

使用@Sujay的方法：

Review.sum("avg_rating * reviews_count") / Review.sum(:reviews_count)