Rails4: How to display the data when association data doesn't exist

Question

What I'd like to do is to display the data as followings;

• Display a.title if a.title exists but @school.rooms.where(day: d).first.name doesn't exist
• Display @school.rooms.where(day: d).first.name if a.title doesn't exist but @school.rooms.where(day: d).first.name exists

It works if both data exist. Although I tried some code such as exist?, nil? and so on, I couldn't.

It would be appreciated if you could give me the best way in Rails.

View code

<div class="row">
  <h1 class="col-md-12"><%= @school.title %></h1>
</div>
<div class="row">

  <% @school.days.each do |d| %>

    <h3>Day<%= d %></h3>

    <% @school.articles.where(day: d).each do |a| %>
      <strong><%= a.title %></strong></p>
    <% end %>

    <p>Room: <%= @school.rooms.where(day: d).first.name %></p>

  <% end %>

</div>

Controller code

class SchoolsController < ApplicationController
  def show
    @school = School.find(params[:id])
  end
end

Model code

class School < ActiveRecord::Base
    has_many :articles
    has_many :rooms

    def days
      self.articles.pluck(:day).uniq
    end
end


class Article < ActiveRecord::Base
    belongs_to :school
end


class Room < ActiveRecord::Base
    belongs_to :school
end

Schema

ActiveRecord::Schema.define(version: 20150999999999) do

  create_table "rooms", force: true do |t|
    t.integer  "school_id"
    t.integer  "day"
    t.string   "name"
    t.string   "detail"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "articles", force: true do |t|
    t.integer  "school_id"
    t.integer  "day"
    t.string   "start_time"
    t.string   "end_time"
    t.integer  "category"
    t.string   "title"
    t.string   "contents"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "schools", force: true do |t|
    t.string   "title"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

It would be appreciated if you could give me any suggestion.

Answer 1

If you will always have either piece of data present (IE a.title exists if @school.rooms.where(day: d).first.name does not), you can use the following:

<p>Room: <%= a.title || @school.rooms.where(day: d).first.name %></p>

If neither exist, you should be able to use a "default" value:

<p>Room: <%= a.title || @school.rooms.where(day: d).first.name || "default" %></p>