RBOnRails-learning/app/controllers/application_controller.rb

class ApplicationController < ActionController::Base
  helper_method :current_user, :logged_in?

  def current_user
    @current_user ||= User.find_by(id: session[:user_id]) if session[:user_id]
  end

  def logged_in?
    !current_user.nil?
  end

  def require_user
    unless logged_in?
      flash[:alert] = "You must be logged in first. Please visit <a href=\"/signup\">the signup page</a> to create an account."
      redirect_to login_path
    end
  end
end