RAILS Faq HowTo Reference Sample Paginate index result and Lookup Table - Foreign Key

1. Introduction

This post gathers information about FAQ-Frequently Asked Question, How To, technical document references and samples about RAILS.

• Paginating index result in Rails
• Lookup Table, Foreign Key, 

2. FAQ, HOWTO, REFERENCES, SAMPLES, etc

2.1. Paginating in RAILS

The will_paginating gem modifies Collection of ActiveRecord to Display Page Links for Querying records. See also:

• https://richonrails.com/articles/getting-started-with-will-paginate
• https://hackhands.com/pagination-rails-will_paginate-gem/
• https://github.com/mislav/will_paginate/wiki
• https://gorails.com/episodes/pagination-with-will-paginate
• http://mislav.github.io/will_paginate/

a) HOWTO

• Step#1: add gem will_paginating

# vim Gemfile
  :
gem 'will_paginate', '~> 3.1.0'
  :

• Step#2: bundle install

# bundle install

• Step#3: Creating MVC for Product and custom controller for paginating each 5 records for page

# rails generate scaffold Product name price:decimal quantity:integer
# vim app/controllers/products_controller.rb
class ProductsController < ApplicationController
  before_action :set_product, only: [:show, :edit, :update, :destroy]
  def index
     @products = Product.all.paginate(page: params[:page], per_page: 5)
  end
   :

• Step#4: Custom index view to paginate

#  vim app/views/products/index.html.erb
   :
</table>
<%= will_paginate @products %>
<br>
   :

• Step#5: Custom CSS stylesheets

# vim app/assets/stylesheets/products.scss
.pagination {
  .previous_page { background:#7777ff; color:white }
  .previous_page.disabled { background: white; color: #777 }
  .current { background: yellow }
  .next_page { background: #7777ff; color: white }
  .next_page.disabled { background: white; color: #777 }
}

• Step#6: Making will_paginate prettier# 

2.2. ActiveRecord Association, Reference, Lookup Table, Foreign Key

This post shows how to create 2 models, where a model referencing another model, on index.html viewer shows attributes from referenced model.

a) HOWTO

• Step#1: Generate 2 models

# rails generate scaffold Author name:string
# rails generate scaffold Book   title:string publishedAt:date author:references

• Step#2: Let's check 2 models created and association

# cat app/models/author.rb
class Author < ApplicationRecord
end

# cat app/models/book.rb

class Book < ApplicationRecord

  belongs_to :author

end

• Step#3: Let's see how books are listed on http:// ... /books. As you can see, author is shown as internal object identification. It's not much pretty, isn't it?

# vim app/views/books/index.html.erb
                   :
        <td><%= book.title %></td>
        <td><%= book.publishedAt %></td>
        <td><%= book.author %></td>
        <td><%= book.author.name %></td>

        <td><%= link_to 'Show', book %></td>
                   :

Books

Title Publishedat Author

Titulo 2017-04-14 #<Author:0x007ff9681cd4f0> Show Edit Destroy

New Book

• Step#4: Adjust app/views/books/index.html.rb to show author name insted of internal object identification

# vim app/views/books/index.html.erb
                   :
        <td><%= book.title %></td>
        <td><%= book.publishedAt %></td>
        <td><%= book.author.name %></td>
        <td><%= book.author.name %></td>

        <td><%= link_to 'Show', book %></td>
                   :

Books

Title Publishedat Author

Titulo 2017-04-14 Machado de Assis Show Edit Destroy

New Book

• Step#5: Adjust app/views/books/show.html.rb to show author name insted of internal object identification

# vim app/views/books/show.html.erb

                   :

<p>
  <strong>Author:</strong>
  <%= @book.author.name %>
</p>

                   :

Books
Title: Titulo
Publishedat: 2017-04-14
Author: Machado de Assis
Edit | Back