Rails的元素添加到陣列

Question

我必須計算出的平均的方法對於給定的記錄：

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陣列。正在打印的賣出期權平均爲：

3.0 
3.0 
3.0 
3.0 
3.0 

如何附加每個評分的被返回到陣列以計算出的平均值，和其他數學函數。

Answer 1

嘗試：

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

您需要先獲得所有您試圖平均的評分。我假設你已經完成了這些操作，並且所有這些評級都存儲在total_rating中。然後，你需要的特定分級添加到該數組：

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

這應該解決您的問題，但有一個更好的辦法

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 

所以給出一組ID，請嘗試以下

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

UPDATE：固定一個行版本

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