application_controller.rb

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

  private

  def require_signin
    unless current_user
      redirect_to new_session_url, alert: 'Please sign in first!'
    end
  end

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

serverlog

..DEPRECATION WARNING: You are passing an instance of ActiveRecord::Base to `find`. Please pass the id of the object by calling `.id`. (called from current_user at /home/andreas/railsdev/dai-ditno/app/controllers/application_controller.rb:14)