Add a Favoriting System to a Rails Project

Have you ever wanted to add a favoriting system to your Rails project? I just recently had a need for this and decided I'd share how I did it.

The Setup

I've been working on a new project at work recently, and I needed a way to allow users to favorite projects. Now, this is something that is quite common with a lot of web applications today and I figured there would be ample documentation on the best way to do this. Unfortunately, I was mistaken.

While I did find a few articles, most of them seemed overly complex. So, with coffee in hand, I sat and pondered this problem for a while.

I have a users model. I have a projects model. I want users to be able to favorite projects. Sounds pretty simple. I could easily do this with a HABTM but I wanted it to be a bit more flexible. What if later, I want users to favorite users?

Okay, so a HABTM wasn't the answer. What I really needed was a polymorphic relationship. A user has many favorites and any other model can be favorited.

The Models

This sounded way too simple. So I set out to test my theory. The first thing I did was to create the favorites table:

bundle exec rails generate model favorite user:references favorited:references{polymorphic}

This creates a migration that looks like this:

class CreateFavorites < ActiveRecord::Migration
  def change
    create_table :favorites do |t|
      t.references :favorited, polymorphic: true, index: true
      t.references :user, index: true


It also generated the model for me, which looks like this:

class Favorite < ActiveRecord::Base
  belongs_to :favorited, polymorphic: true
  belongs_to :user

After running rake db:migrate, I moved onto the user model. I wanted to be able to get all the favorites, but I also wanted a way of returning just favorited projects. This will come in handy later when I start adding other models to the favoriting system. Again, this is pretty simple to do:

class User < ActiveRecord::Base
  has_many :favorites
  has_many :favorite_projects, through: :favorites, source: :favorited, source_type: 'Project'

That is literally all you have to do with regards to the models. You can now CRUD favorites. If the favorited relationship happens to be a project, on the user object you can now call user.favorite_projects and it will return only favorited projects. Neat.

The Controller

I didn't want to muck up the users controller or the projects controller with favoriting details. The act of creating a "favorite" isn't really the responsibility of either the user or the project.

Instead, I created a completely separate resource called favorite_projects. In the future, I will probably make this more generic, but for now, users will only be able to favorite projects. I had to add a new line in the routes file to make this happen and also wanted to ensure that only create and destroy actions were supported:

resources :favorite_projects, only: [:create, :destroy]

Finally, I created the controller which would use the current_user method to set the user for the favorite instance. For the create action, I passed a param called project_id since an id in the params hash for create wouldn't work. For that reason, I have to find the project based on either params[:id] or params[:project_id]. Here is the entire FavoriteProjectsController:

class FavoriteProjectsController < ApplicationController
  before_action :set_project
  def create
    if Favorite.create(favorited: @project, user: current_user)
      redirect_to @project, notice: 'Project has been favorited'
      redirect_to @project, alert: 'Something went wrong...*sad panda*'
  def destroy
    Favorite.where(favorited_id:, user_id:
    redirect_to @project, notice: 'Project is no longer in favorites'
  def set_project
    @project = Project.find(params[:project_id] || params[:id])

In Closing

Now, all I have to do in order to use this feature is generate a create or delete URL:

<%- unless current_user.favorite_projects.exists?(id: -%>
<%= link_to 'Add to favorites', favorite_projects_path(project_id: @project), method: :post %>
<%- else -%>
<%= link_to 'Remove from favorites', favorite_project_path(@project), method: :delete %>
<%- end -%>

The best part about this is that I can easily modify this to accept any other model in my app that should have favoriting. I hope this is helpful to anyone reading this. Let me know if you use this technique or if I missed anything.

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