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     id_column = "#{items.table_name}.id"
  10     page_items = if params[:before]
  11                    items.where("#{id_column} < ?", params[:before]).order(:id => :desc)
  12                  elsif params[:after]
  13                    items.where("#{id_column} > ?", params[:after]).order(:id => :asc)
  14                  else
  15                    items.order(:id => :desc)
  16                  end
  17
  18     page_items = page_items.limit(limit)
  19     page_items = page_items.includes(includes)
  20     page_items = page_items.sort.reverse
  21
  22     newer_items_id = page_items.first.id if page_items.count.positive? && items.exists?(["#{id_column} > ?", page_items.first.id])
  23     older_items_id = page_items.last.id if page_items.count.positive? && items.exists?(["#{id_column} < ?", page_items.last.id])
  24
  25     [page_items, newer_items_id, older_items_id]
  26   end
  27 end