[Ruby on Rails] Posting score ranking function (whole display)

Target

--Ranking of user posts --Summing / averaging the evaluation points for posts, and ranking the posting points of the posting user. --Post score ranking (possible if you change the user part to post) ――The score ranking of the post by totaling / averaging the evaluation scores for the post

Development environment

ruby 2.5.7 Rails 5.2.4.3 OS: macOS Catalina

Premise

• If you select ▶ ◯◯, explanations will be displayed. I hope you can refer to it if you are not sure.

-Build login environment with devise -Posting function that only logged-in users can do -Post editing function (update, delete)

• To be able to display users who do not have a numerical value yet Implement the ranking function using left_joins and sort_by.
• There are other ranking methods, so I will post them as needed.

Add column

Added to give a rating in the comments to the post.

Terminal

$ rails g migration AddScoreToComments score:integer

db/migrate/xxxxxxxxxxxxx_add_score_to_comments.rb

class AddScoreToComments < ActiveRecord::Migration[5.2]
  def change
    add_column :comments, :score, :integer, default: 0
  end
end

If nothing is done, there will be a difference in points, so Described so that the score can be selected in view.

erb:app/views/posts/show.html.erb

Evaluation:<%= f.number_field :score,min:1,max:5 %>

When giving the total value

<% @sum = 0 %>
<% @post.comments.each do |comment| %>
  <% @sum += comment.score %>
<% end %>
<%= @sum %>

When calculating the average value

<% @average = 0 %>
<% @post.comments.each do |comment| %>
  <% @average += (comment.score / @user.comments.count) %>
<% end %>
<%= @average %>

Now that we're ready, let's move on to the main topic.

controller The controller is the key.

Total value ranking: app/controllers/users_controller.rb

  def rank
    @users = User.
              left_joins(:comments).
              distinct.
              sort_by do |user|
                hoges = user.comments
                if hoges.present?
                  hoges.map(&:score).sum
                else
                  0
                end
              end.
              reverse
  end

Mean ranking: app/controllers/users_controller.rb

  def rank
    @users = User.
              left_joins(:comments).
              distinct.
              sort_by do |user|
                hoges = user.comments
                if hoges.present?
                  hoges.map(&:score).sum / hoges.size
                else
                  0
                end
              end.
              reverse
  end

view Can be displayed in descending order of each as shown below After creating app / views / users / rank.html.erb

erb:app/views/users/rank.html.erb

<% @users.each do |user| %>
  <%= link_to user_path(user) do %>
    <%= user.name %><br>
  <% end %>
<% end %>

routing

config/routes.rb

get '/rank', to: 'users#rank'

Reference site

[Easy ranking function with Rails] (https://qiita.com/mitsumitsu1128/items/18fa5e49a27e727f00b4) [Rails] Implementation of ranking function

Summary

This time I wanted to show the users who posted high scores, so Although it became such a description, It may not be very practical. However, if you use these rankings, Only for those who appreciate the score or only for those who have a low score I think it's a sales-friendly ranking because you can take an approach.

Also, if you want to implement word-of-mouth ranking etc. for the score ranking of posts, I think it will be a practical description.