{"id":8717,"date":"2023-09-28T11:33:32","date_gmt":"2023-09-28T11:33:32","guid":{"rendered":"https:\/\/www.bacancytechnology.com\/qanda\/?p=8717"},"modified":"2023-10-26T07:21:53","modified_gmt":"2023-10-26T07:21:53","slug":"listing-categories-with-associated-books-in-a-ruby-on-rails","status":"publish","type":"post","link":"https:\/\/www.bacancytechnology.com\/qanda\/ruby-on-rails\/listing-categories-with-associated-books-in-a-ruby-on-rails","title":{"rendered":"Listing Categories with Associated Books in a Ruby on Rails Digital Library"},"content":{"rendered":"

Setting Up the Relationship<\/h3>\n

First, let’s establish the relationship between categories and books in the Rails model.
\nMake sure that the setup of models is like this:
\nCategory Model<\/strong><\/p>\n

class Category < ApplicationRecord\r\n  has_many :books\r\nend\r\n<\/pre>\n
Book Model<\/strong><\/p>\n
class Book < ApplicationRecord\r\n  belongs_to :category\r\nend\r\n<\/pre>\n
With this setup, each category can have multiple books associated with it.<\/p>\n
Fetching Categories and Books<\/strong><\/p>\n
Now, let’s move on to the controller. In the controller’s index action, we want to fetch all categories along with their associated books. To do this efficiently and avoid the N+1 query problem, we can use the includes method:<\/p>\n
# Categories controller\r\n\r\ndef index\r\n  @categories = Category.includes(:books).all\r\nend\r\n<\/pre>\n
Displaying Categories and Books<\/strong><\/p>\n
In your view, loop through the categories and their associated books and display them as desired.
\nHere’s an example view:<\/p>\n
<!-- Categories view -->\r\n<% @categories.each do |category| %>\r\n  <h2><%= category.name %><\/h2>\r\n  <ul>\r\n    <% category.books.each do |book| %>\r\n      <li><%= book.name %><\/li>\r\n    <% end %>\r\n  <\/ul>\r\n<% end %>\r\n<\/pre>\n
In this view:<\/p>\n
    \n
  • We loop through @categories to iterate over each category.<\/li>\n
  • Inside the category loop, we display the category name using an <h2> heading.<\/li>\n
  • We use an unordered list (<ul>) to display the associated books as list items (<li>).<\/li>\n
  • We use category.books.each to loop through the books associated with the current category and display their names.<\/li>\n<\/ul>\n
    Adding Links to Book Names<\/strong><\/p>\n
    If needed, we can add links to the book names. We can modify the view like this:<\/p>\n
    <!-- Categories view for Book Names with Links -->\r\n<% @categories.each do |category| %>\r\n  <h2><%= category.name %><\/h2>\r\n  <ul>\r\n    <% category.books.each do |book| %>\r\n      <li><%= link_to book.name, book %><\/li>\r\n    <% end %>\r\n  <\/ul>\r\n<% end %>\r\n<\/pre>\n
    Now, the book names will be displayed as links that lead to the respective book’s details page.<\/p>\n","protected":false},"excerpt":{"rendered":"
    Setting Up the Relationship First, let’s establish the relationship between categories and books in the Rails model. Make sure that the setup of models is like this: Category Model class Category < ApplicationRecord has_many :books end Book Model class Book < ApplicationRecord belongs_to :category end With this setup, each category can have multiple books associated […]<\/p>\n","protected":false},"author":1,"featured_media":8908,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[11],"tags":[],"class_list":["post-8717","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ruby-on-rails"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/posts\/8717"}],"collection":[{"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/comments?post=8717"}],"version-history":[{"count":5,"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/posts\/8717\/revisions"}],"predecessor-version":[{"id":8722,"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/posts\/8717\/revisions\/8722"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/media\/8908"}],"wp:attachment":[{"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/media?parent=8717"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/categories?post=8717"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bacancytechnology.com\/qanda\/wp-json\/wp\/v2\/tags?post=8717"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}