tab/app/controllers/users_controller.rb

class UsersController < ApplicationController
  load_and_authorize_resource

  def show
    @user = User.find(params[:id])
    respond_to do |format|
      format.html
      format.json do
        datatable = DataTable.new(@user, params)
        render json: datatable.json
      end
    end
  end

  def index
    @users = User.all
  end
end