Export to CSV

# Model
    def self.to_csv(data, options = {})
      desired_columns = ["id", "name", "phone", "email", "created_at"]
      CSV.generate(options) do |csv|
        csv << desired_columns
        data.each do |u|
          csv << u.attributes.values_at(*desired_columns)
        end
      end
    end

# Controller
    def index
      params = filter_params

      users= UserServices.fetch_data(params)
      @users = users.paginate(:page => params[:page], :per_page => 50)
      respond_to do |format|
        format.html
        format.csv { send_data UserServices.to_csv(users) }
      end
    end

# View
    %form{method: :GET}
        .small-4.columns
          .small-6.columns
            %input.button.small{:type => "submit", :value => "Thực hiện"}
          .small-6.columns
            =link_to 'Export', user_index_path(format: "csv"), class: 'button small', id: 'user-export'