class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception

  before_filter :authenticate

  protected

  def authenticate
    if Rails.env.production?
      authenticate_or_request_with_http_basic do |username, password|
        username == ENV['HTTP_AUTH_USERNAME'] && password == ENV['HTTP_AUTH_PASSWORD']
      end
    end
  end
end

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception

  before_action :authenticate

  protected

  def authenticate
    if Rails.env.production?
      authenticate_or_request_with_http_basic do |username, password|
        username == ENV['HTTP_AUTH_USERNAME'] && password == ENV['HTTP_AUTH_PASSWORD']
      end
    end
  end
end

Use before_action instead of before_filter
Use before_action instead of before_filter
