Refactor datatable class to a controller concern

app/controllers/admin/users_controller.rb

@@ -1,16 +1,19 @@
 module Admin
   class UsersController < Admin::BaseController
     load_and_authorize_resource
+    include DatatableServersideProcessing
 
     def new
       @user = User.new
     end
 
     def index
-      users_datatable = Datatable.new(view_context, User.where(nil), %w(name email), %w(id state email name))
+      @users = filtered_records(User.where(nil), %w(name email), %w(id state email name))
       respond_to do |format|
         format.html
-        format.json { render json: users_datatable.to_json(data: users_datatable.paginated_records.map {|user| users_datatable_data(user)}) }
+        format.json do
+          render json: datatable_response(@users.map {|user| users_datatable_data(user)})
+        end
       end
     end
 

app/controllers/concerns/datatable_serverside_processing.rb

@@ -0,0 +1,44 @@
+module DatatableServersideProcessing
+  extend ActiveSupport::Concern
+
+  def datatable_response(data)
+    {
+      sEcho: params[:sEcho].to_i,
+      iTotalRecords: @collection.count,
+      iTotalDisplayRecords: records.count,
+      aaData: data
+    }
+  end
+
+  def filtered_records(collection, search_columns, sort_columns)
+    @collection = collection
+    @search_columns = search_columns
+    @sort_columns = sort_columns
+    paginate(records)
+  end
+
+  private
+
+  def records
+    @records ||= fetch_records
+  end
+
+  def fetch_records
+    sort_direction = params[:sSortDir_0] == 'desc' ? 'desc' : 'asc'
+    sort_column = @sort_columns[params[:iSortCol_0].to_i]
+    records = @collection.order("#{sort_column} #{sort_direction}")
+
+    if params[:sSearch].present? && @search_columns.present?
+      search_query = @search_columns.map{ |column|  "#{column} like :search" }.join(' or ')
+      records = records.where(search_query, search: "%#{params[:sSearch]}%")
+    end
+
+    records
+  end
+
+  def paginate(records)
+    per_page = params[:iDisplayLength].to_i > 0 ? params[:iDisplayLength].to_i : 10
+    page = params[:iDisplayStart].to_i / per_page + 1
+    records.offset((page - 1) * per_page).limit(per_page)
+  end
+end