Trouble Creating and showing Users in Rails blog - ruby-on-rails

Question

I keep getting a variety of error while trying to create and show errors in a simple Rails blog I'm trying to create.Let me know if you see anything obvious or if you need me to post more code as I've tried a number of things but to no avail. Thanks
The browser is giving me this error
Couldn't find User without an ID
in my "logged_in?" method which shows
def logged_in?
#current_user ||= User.find(session[:user_id])
end
Sessions Controller
class SessionsController < ApplicationController
def new
end
def create
user = User.find_by(email: params[:email])
if user && user.authenticate(params[:password])
session[:user_id] = user.id
flash[:success] = "You are logged in"
redirect_to root_path
else
render action: 'new'
flash[:error] = "There was a problem logging in. Please check your email and password"
end
end
end
def index
#users = User.all
end
def show
end
def new
#user = User.new
end
def edit
end
def create
#user = User.new(user_params)
if #user.save
session[:user_id] = #user.id
flash[:notice] = "You have registered, please login"
redirect_to login_path
else
render :new
end
end
def update
respond_to do |format|
if #user.update(user_params)
format.html { redirect_to #user, notice: 'User was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: 'edit' }
format.json { render json: #user.errors, status: :unprocessable_entity }
end
end
end
def destroy
#user.destroy
respond_to do |format|
format.html { redirect_to users_url }
format.json { head :no_content }
end
end
private
def set_user
#user = User.find(params[:id])
end
def user_params
params.require(:user).permit(:first_name, :last_name, :email, :password, :password_confirmation)
end
end
Articles Controller
class ArticlesController < ApplicationController
http_basic_authenticate_with name: "dhh", password: "secret", except: [:index, :show]
def new
#article = Article.new
end
def index
#article = Article.all
end
def create
#article = Article.new(article_params)
if #article.save
redirect_to #article
else
render 'new'
end
end
def edit
#article = Article.find(params[:id])
end
def update
#article = Article.find(params[:id])
if #article.update(article_params)
redirect_to #article
else
render 'edit'
end
end
def show
#article = Article.find(params[:id])
end
def destroy
#article = Article.find(params[:id])
#article.destroy
redirect_to articles_path
end
private
def article_params
params.require(:article).permit(:title, :text, :image)
end
end
Application Helper
module ApplicationHelper
def logged_in?
#current_user ||= User.find(session[:user_id])
end
end

Answer 1

The problem you're facing is that session[:user_id] is nil. Usually a method which sets current user is called current_user. The logged_in? is not a good name for a method setting an user instance, because one would expect that a method ending with a question mark would return a true or false. And not an user instance.
Also, setting the current user is usually done with a before_filter. Additionally, you want to skip such before filter for action where you're setting the current user (i.e the current_user doesn't exist yet)
Finally, I would rather fail gracefully, if user is not found. You can achieve this by changing your code to User.find_by_id(session[:user_id])

Answer 2

While the user is not loggued, session[:user_id] is nil, and so User.find(session[:user_id]) generates the error. The method should be like this:
def logged_in?
#current_user ||= User.find(session[:user_id]) if session[:user_id].present?
end

Answer 3

Why would the logged_in? helper method try to assign a value to #current_user? I think that is a bad logic, it should just return a boolean result without modifying such a central instance. This is a proper way to do that:
def logged_in?
#current_user.nil? ? false : true
end
The responsibility of setting the #current_user falls to a method that you should place in application_controller.rb and make it a before_action so that it's executed before any controller action is triggered, that is:
# app/controllers/applicaton_controller.rb
class ApplicationController < ActionController::Base
protect_from_forgery
before_action :authenticate_user
# Your actions here
..
..
#
private
def authenticate_user
#current_user ||= User.find(session[:user_id]) if session[:user_id].present?
end
end