Rails4：如何在关联表中显示名称？

Question

What I'd like to do is to display the name in the details table.

I tried some codes, but I couldn't. Please advise me on how to display the value.

Controller code:

class BooksController < ApplicationController
  def show
    @book = Book.find(params[:id])
    @article = Article.where(book_id: (params[:id])).order(day: :asc)
  end
end

View code:

<div class="row">
  <% @article.each do |a| %>
    <%= a.day %><br>
    <%= a.title %><br>
    # want to display the name in detail table where (details.day = articles.day and details.book_id = articles.book_id)
  <% end %>
</div>

Relevant model setup:

class Article < ActiveRecord::Base
    belongs_to :Book
    default_scope -> { order(day: :asc, start_time: :asc) }
end

class Detail < ActiveRecord::Base
    belongs_to :Book
end

class Book < ActiveRecord::Base
    has_many :articles
    has_many :details
end

Schema:

ActiveRecord::Schema.define(version: 2015099999999) do

  create_table "details", force: true do |t|
    t.integer  "book_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  "book_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 "books", force: true do |t|
    t.date     "publish_date"
    t.string   "title"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

end

Answer 1

You want to define an association between Article and Detail using the :through option:

class Article < ActiveRecord::Base
  belongs_to :book
  has_many :details, through: :book
end

You can also define an accessor to find just the detail for the matching day:

class Article < ActiveRecord::Base
  def matching_detail
    details.find_by_day day
  end
end

Which you can then use in the view:

<% @article.each do |a| %>
  <%= a.matching_detail.try(:name) %>
<% end %>

Answer 2

It's good to define the associations for articles like

has_many :details, through: :book

You can also also use this .

Article.includes(:details).where(book_id: (params[:id])).order(day: :asc)

Or

Article.select('articles.name,details.name,..').joins(:details).where([condition])