app/controllers/concerns/pagination_methods.rb

   1 module PaginationMethods
   2   extend ActiveSupport::Concern
   3
   4   private
   5
   6   ##
   7   # limit selected items to one page, get ids of first item before/after the page
   8   def get_page_items(items, includes: [], limit: 20)
   9     param! :before, Integer, :min => 1
  10     param! :after, Integer, :min => 1
  11
  12     id_column = "#{items.table_name}.id"
  13     page_items = if params[:before]
  14                    items.where("#{id_column} < ?", params[:before]).order(:id => :desc)
  15                  elsif params[:after]
  16                    items.where("#{id_column} > ?", params[:after]).order(:id => :asc)
  17                  else
  18                    items.order(:id => :desc)
  19                  end
  20
  21     page_items = page_items.limit(limit)
  22     page_items = page_items.includes(includes)
  23     page_items = page_items.sort.reverse
  24
  25     newer_items_id = page_items.first.id if page_items.count.positive? && items.exists?(["#{id_column} > ?", page_items.first.id])
  26     older_items_id = page_items.last.id if page_items.count.positive? && items.exists?(["#{id_column} < ?", page_items.last.id])
  27
  28     [page_items, newer_items_id, older_items_id]
  29   end
  30 end