Rails的元素添加到阵列

Question

我必须计算出的平均的方法对于给定的记录：

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不被追加到total_rating阵列。正在打印的卖出期权平均为：

3.0 
3.0 
3.0 
3.0 
3.0 

如何附加每个评分的被返回到阵列以计算出的平均值，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

您需要先获得所有您试图平均的评分。我假设你已经完成了这些操作，并且所有这些评级都存储在total_rating中。然后，你需要的特定分级添加到该数组：

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 

Answer 3

这应该解决您的问题，但有一个更好的办法

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 

所以给出一组ID，请尝试以下

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

UPDATE：固定一个行版本

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