Pagination in Rails can be implemented easily with will_paginate gem. will_paginate modifies Collection of ActiveRecord in a way to implement pagination.

What is will_paginate?

• It is Pagination Library for Rails
• Querying for Records and Displaying Page Links can be automated using this gem
• Source: Github - will_paginate

Below given are steps for integration of will_paginate with Rails.

Step 1: Add to Gemfile

Add gem will_paginate in your Gemfile

gem 'will_paginate'

This will ensure latest version of gem ‘will_paginate’ being used with your Rails Application

Step 2: Bundle Install

Perform Bundle Install of your Rails Project

bundle install

This command needs to be executed in Rails Application directory which will install gem ‘will_paginate’ in your Ruby environment if already not installed. If this gem is already available in your environment then it will just use the gem will Rails Application.

Step 3: Code Changes for Basic Integration

Suppose, we have User Model in database and we are displaying all Users in show.erb file. We need pagination for the same. This can be implemented in following way.

Controller - Action changes

Add pagination parameter to the Model which is being queried for the Paginated result set.

Why?

It adds necessary parameters in the resultant collection of record to display pagination links in front-end (.erb)

Parameters that are added -

• current_page - the page number for current paginated result data set
• total_entries - numbers of records in database satisfying given criteria
• limit - per page limit for the paginated result data
• offset - current paginated data set -> to show current page

class UserController < ApplicationController
   def show
       # added some condition for where clause
       @users = User.where('age > ?', 18).paginate(:page => params[:page], :per_page => 5)
   end
end

Parameter:

• :page - This is parameter sent in Query String. Based on this, which records are to be fetched is decided. i.e. Offset is decided.
• :per_page - This is Number of results that you want to fetch per page i.e. From offset

ERB - show.erb

This is just displaying the paginated result on front-end. For Awesome UI Elements on front-end you can refer Semantic UI Rails Integration

You can inspect @users by debugging and you will find current_page, total_entries, limit, offset** with the variable **@users that help in displaying pagination links by will_paginate as given below.

Step 4. Adding Pagination Links

<%= will_paginate @users %>

It will add pagination links like,

on front-end. Number of Pages here 817, 818 is decided based on total numbers of records that you have in your database.

Extra -

Adding Custom Parameters in will_paginate AJAX Request

You can add custom parameters in AJAX request send by will_paginate for getting paginated result. You can do this like,

<%= will_paginate @users, :params => {:is_active: true} %>

This will send is_active=true as a parameter in the query string.

Query string would become as https://someurl.com/?page=2&is_active=true

This way you can send multiple custom parameters with AJAX request of will_paginate

Performing Javascript/JQuery Operation before AJAX request

Sometimes you might need to perform some Javascript/JQuery operation (E.g. Showing loader while the request fetches result from Backend) before you send AJAX request to get paginated result. This can be achieved by,

Enclose the pagination code of erb in div tag, like

Then you can use will_paginate_id for performing javascript operation like,

Conclusion - Pagination in Rails

• We illustrated the easiest way of implementing Pagination in Rails using will_paginate gem
• Let us know through comments if you face any difficulties implementing the same or any other problem while using the gem for implementing pagination in rails.