[Rails] List instances of multiple models

What you want to do

Like the YouTube and Facebook timelines, we needed the ability to display posts and ads on the same screen in descending order of creation (usually ads may not be in order of creation, but to keep things simple. (Assuming that they are arranged in the order of creation).

Let's think about how to get the post model (Post) and the advertisement model (Advertisement) well with the controller and process them in parallel in the view.

Premise

version

• Ruby 2.6.3
• Rails 5.2.3

Columns of each model

#Posting model and advertising model have different columns

#Post model (Post)
  t.integer "user_id"
  t.string "content"
  t.string "image"
  t.datetime "created_at"
  t.datetime "updated_at"

#Advertising model (Advertisement)
  t.integer "company_id"
  t.string "content"
  t.string "link_url"
  t.datetime "expired_date"
  t.datetime "created_at"
  t.datetime "updated_at"

Implementation method

timeline_controller.rb

def index
  posts = Post.all
  ads = Advertisement.all

  #Make each multiple instance into one array
  @instances = posts | ads
  #Sort in descending order of creation
  @instances.sort!{ |a, b| b.created_at <=> a.created_at }
end

erb:index.html.erb

<% @instances.each do |instance| %>
  <% if instance.class == "Post" %>
    <%#Post display%> 
    <%= instance.user_id %>
    <%= instance.content %>
    <%= instance.image %>
  <% else %>
    <%#Display Advertisement%> 
    <%= instance.company_id %>
    <%= instance.content %>
    <%= instance.link_url %>
  <% end %>
<% end %>