Final result:

  • whenever you visit a movie page, it will be added to “recently opened movie pages” list
  • 5 last opened movies will be saved in the list
  • list is unique for each user

kredis-recently-viewed.gif

1. Initial setup for the app #

First, let’s mimic a current_user without installing Devise:

# Terminal
rails g model User session:string
rails db:migrate

class ApplicationController < ActionController::Base
  helper_method :current_user

  def current_user    
    @current_user ||= User.find_or_create_by(session: session.id.to_s)
  end
end

Next, lets add a Movies table:

# Terminal
./bin/rails g scaffold movie title
rails db:migrate
bundle add faker
rails c
20.times { Movie.create!(title: Faker::Movie.title) }

Install kredis:

# Terminal
./bin/bundle add kredis
./bin/rails kredis:install

2. recently opened pages with Kredis #

Kredis.unique_list is basically an array with a max number of elements:

ab = Kredis.unique_list("recent")
ab.limit = 5
ab.elements
# []
ab.prepend(Movie.first.id)
# ["1"]
ab.prepend(Movie.last.id)
# ["1", "20"]
ab.elements
# ["1", "20"]
ab.prepend(20)
# ["20", "1"]
ab.remove(["20", "1"])
# []

Add a kredis column association to User:

# app/models/user.rb
class User < ApplicationRecord
  kredis_unique_list :recent_movies, limit: 5
end

Next, when the user opens the page, prepend (add to start of list) the movie.id to current_user.recent_movies:

# app/controllers/movies_controller.rb
class MoviesController < ApplicationController
  def show
    @movie = Movie.find(params[:id])
    current_user.recent_movies.prepend(@movie.id)
    # current_user&.recent_movies.clear # clear array
    # current_user.recent_movies.remove(current_user.recent_movies.elements) # stupid clear array
  end
end

Display the list:

# app/views/users/_recently_opened_movies.html.erb
<% current_user.recent_movies.elements.each do |movie| %>
  <% movie = Movie.find(movie) %>
  <%= link_to movie.title, movie_path(movie) %>
<% end %>

That’s it!