Ruby on Rails || Following conferences - ruby-on-rails

Question

I'm trying to create an app in Ruby on Rails where I can:
Create conferences (working)
See a listing of conferences (working)
Follow and unfollow a conference (not working)
View a following conference (not working)
I've started working with Ruby on Rails back in December and used Micheal Hartl's tutorial to get started. In chapter 14 (https://www.railstutorial.org/book/following_users) Micheal introduces following and unfollowing users, trough relationships.
I'm trying to apply his techniques, but adjusting it to where you have a relation between one model and one controller, to where there are two models and two controllers.
One controller & model is the User_controller and the User Model, the other controller & model are the Conference_controller and the Conference Model.
I started by adding active relations to the User Model, since it's the party that's following the conferences
user.rb
has_many :active_relationships, class_name: "Relationship",
foreign_key: "follower_id",
dependent: :destroy
has_many :following, through: :active_relationships, source: :followed
I've done the opposite in the Conference Model, because i'ts the party thats being followed
Conference.rb
has_many :passive_relationships, class_name: "Relationship",
foreign_key: "followed_id",
dependent: :destroy
has_many :followers, through: :passive_relationships, source: :follower
To make the structure cleared I've added to following line of code to the Relationship model
Relationship.rb
belongs_to :follower, class_name: "User"
belongs_to :followed, class_name: "Conference"
validates :follower_id, presence: true
validates :followed_id, presence: true
When trying to see if the user is actually following the conference an error occurs in the User model stating:
ActiveRecord::RecordNotUnique in RelationshipsController#create
SQLite3::ConstraintException: UNIQUE constraint failed: relationships.follower_id, relationships.followed_id: INSERT INTO "relationships" ("follower_id", "followed_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)
The root of the problem lies in:
app/models/user.rb:116:in `follow'
app/controllers/relationships_controller.rb:6:in `create'
I understand that the problem occurs when a record cannot be inserted because it would violate a uniqueness constraint, but I don't know what uniqueness constraint is being violated.
Now the first problem happens in the user.rb, when an active_relationship is being created between user and conference.
# Returns true if the current user is following the other user.
def following?(other_conference)
following.include?(other_user)
end
# Follows a conference.
def follow(other_conference)
active_relationships.create(followed_id: other_conference.id)
end
# Unfollows a conference.
def unfollow(other_conference)
active_relationships.find_by(followed_id: other_conference.id).destroy
end
The second problem is in the Relationships_controller, where the current_user should follow the conference.
def create
#conference = Conference.find(params[:followed_id])
current_user.follow(#conference)
respond_to do |format|
format.html { redirect_to #conference }
format.js
end
end
Now i'm not sure what the cause of the problem is and how to solve it. I hope I've made my problem clear and what i'm trying to achieve. If not I would gladly give more information concerning my problem.

Answer 1

You're following an example that handles a more complex case (where you're joining the same table twice) and your solution is a bit more complicated than it needs to be:
class User
has_many :subscriptions
has_many :conferances, though: :subscriptions
def subscribed_to?(conference)
conferances.include?(conference)
end
def find_subscription(conference)
subscriptions.find_by(conference: conference)
end
end
class Conferance
has_many :subscriptions
has_many :users, though: :subscriptions
end
# Its better to name join models after an actual thing
class Subscription
belongs_to :user
belongs_to :conference
end
resources :conferences, shallow: true do
resource :subscriptions, only: [:create, :destroy]
end
class SubscriptionsController
before_action :set_conferance, only: :create
def create
if current_user.subsciptions.create(conferance: #conferance)
flash[:success] = "You are now subscribed to { #conferance.name }"
else
flash[:error] = "Could not create subscription."
end
redirect_to #conferance
end
def destroy
#subscription = current_user.subsciptions.find(params[:id])
if #subscription.destroy
flash[:success] = "You are no longer subscribed to { #conferance.name }"
else
flash[:error] = "Oh noes"
end
redirect_to #subscription.conferance
end
def set_conferance
#conferance = Conferance.find(params[:conferance_id])
end
end
<% if current_user.subscribed_to?(#conferance) %>
<%= button_to "Subscribe", conferance_subsciptions_path(#conferance), method: :post %>
<% else %>
<%= button_to "Unsubscribe", subscription_path(current_user.find_subscription(#conferance)), method: :delete %>
<% end %>