ruby-on-rails - Rails 向数组添加元素

Question

我有一种方法可以计算给定记录集的平均值：

input = params[:recommendation_ratings].values  # The params are sent from radio_tags in my view.

input.each do |mini_params|
rating_id = mini_params[:rating_id]
l = Rating.find(rating_id) #Find record on Rating table. 
l.rating #Get value associated with rating_id
total_rating = []
total_rating << l.rating
average = total_rating.inject{ |sum, el| sum + el }.to_f / total_rating.size
puts average
end

l.rating 未附加到 total_rating 数组。看跌平均值打印为：

3.0
3.0
3.0
3.0
3.0

如何将返回的每个评级附加到数组中以计算平均值和其他数学函数。

Answer 1

尝试：

total_rating = []    
input.each do |mini_params|
  rating_id = mini_params[:rating_id]
  l = Rating.find(rating_id) #Find record on Rating table. 
  total_rating << l.rating      
end
average = total_rating.sum / total_rating.size.to_f

Answer 2

这应该可以解决您的问题，但有更好的方法

total_rating = []    
input.each do |mini_params|
  rating_id = mini_params[:rating_id]
  l = Rating.find(rating_id) #Find record on Rating table. 
  total_rating << l.rating
  average = total_rating.inject(:+).to_f / total_rating.size
  puts average
end

因此，给定一个 id 数组，请尝试以下操作

Rating.where(id: mini_params[:rating_id]).average(:rating)

更新：修复单行版本

rating_ids = input.map { |mini_params| mini_params[:rating_id] }
Rating.where(id: rating_ids).average(:rating)

Answer 3

您需要首先获得您想要平均的所有评级。我假设您已经这样做了，并且所有这些评级都存储在total_rating. 然后您需要将特定评级添加到该数组：

rating_id = mini_params[:rating_id]
l = Rating.find(rating_id)
total_rating << l
average = total_rating.sum.to_f / total_rating.size
puts average