Since a lot of my past projects included some sort of single-page application as the frontend and Rails as the backend, I wanted to check how hard would it be to implement pagination without using any gems.
Turns out it’s not that hard.
module Pagination
def self.per_page
25
end
scope :paginate, ->(page){
offset = [page.to_i - 1, 0].max * per_page
offset(offset).limit(per_page)
} do
def total
except(:limit, :offset).count(:all)
end
def current_page
page
end
def total_pages
(total.to_f / per_page).ceil
end
def more_available?(page)
page = [page.to_i, 1].max
page < total_pages
end
end
end
Include this in any Active Record model and it’s good to go.
class User < ApplicationRecord
extend Pagination
end
User.paginate(3) # third page of users
class User < ApplicationRecord
scope(:admin), -> { where(:role, :admin) }
end
User.admin.paginate(2) # second page of users that are admins
Unlike most popular pagination libraries for Rails, this implementation does not deal with the view layer, since it’s assumed that this is going to be implemented within the SPA.