Rollback transaction rails console - ruby-on-rails

Question

I have encountered a problem with my rails console when I try to create a new event based on a user. I have a feeling this is a very simple error that I am getting, but I am posting because I am unsure of how I should fix it. Here is the command I tried to run:
user.event = Event.create(:name => "Dummy")
Here is my db file for my event:
class CreateEvents < ActiveRecord::Migration[5.0]
def change
create_table :events do |t|
t.string :name
t.timestamps
end
end
end
Here is my Users database file:
class CreateUsers < ActiveRecord::Migration[5.0]
def change
create_table :users do |t|
t.string :name
t.string :email
t.string :event
t.integer :code
t.timestamps
end
end
end
Here is my User.rb file:
class User < ApplicationRecord
has_secure_password
has_many :events
def User.digest(string)
cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST : BCrypt::Engine.cost
BCrypt::Password.create(string, cost: cost)
end
end
Here is my Event.rb file:
class Event < ApplicationRecord
belongs_to :user
end

Answer 1

Its not a simple error. It's quite a few things which are wrong.
If you want a relation where a user can have many events, and an event can belong to many users you need to create a join table. As storing a foreign key on either the users or events table would create a one to many relationship which is probably not what you want.
class User < ApplicationRecord
has_many :user_events
has_many :events, through: :user_events
end
class Event < ApplicationRecord
has_many :user_events
has_many :users, through: :user_events
end
# this is a join model.
class UserEvent < ApplicationRecord
belongs_to :user
belongs_to :event
end
A has_many :through association is often used to set up a many-to-many
connection with another model. This association indicates that the
declaring model can be matched with zero or more instances of another
model by proceeding through a third model.
http://guides.rubyonrails.org/association_basics.html#the-has-many-through-association
You can generate the UserEvent model and the migration which creates the join table by running:
rails g model user_event user:belongs_to event:belongs_to
This will create a user_events table with the user_id and event_id foreign key columns. You should also roll back the migration which creates the users table and fix it:
class CreateUsers < ActiveRecord::Migration[5.0]
def change
create_table :users do |t|
t.string :name
t.string :email
t.string :password_digest # !!!
t.integer :code
t.timestamps
end
end
end
Note the addition of the password_digest column - this is required for has_secure_password. If you have already run this migration on the production database or committed and pushed it you should instead create separate migrations which fix the errors:
class AddPasswordDigestToUsers < ActiveRecord::Migration[5.0]
def change
add_column(:users, :password_digest, :string)
end
end
class RemoveEventFromUsers < ActiveRecord::Migration[5.0]
def change
remove_column(:users, :event)
end
end
To create an event which is associated with a user you can do:
event = user.events.new(name: "Dummy") # does not persist the record
event = user.events.create(name: "Dummy")
You can all assign records from either end by using the shovel operator:
user.events << event
event.users << user
Is this the right association for me?
My main goal for my application is to make it so a user has partys and
those parties have songs.
A party with only one user sounds pretty lame. However if you want to create a special relationship for the user you can create a separate association:
class User < ApplicationRecord
has_many :user_events
has_many :events, through: :user_events
has_many :owned_events, class_name: 'Event', foreign_key: 'owner_id'
end
class Event < ApplicationRecord
has_many :user_events
has_many :users, through: :user_events
belongs_to :owner, class_name: 'User'
end
class AddOwnerIdToEvents < ActiveRecord::Migration[5.0]
def change
add_column(:events, :owner_id, :integer)
add_foreign_key(:events, :users, column: :owner_id)
end
end
Another way to solve this is by adding a column to UserEvent join model which specifies what the association is. But this is pretty far beyond your skill level.

Answer 2

There is no foreign key in your tables. Supposing you are actually intending to have the models as explained ("event belongs to user"/"user has many events"), you need to add a column user_id to the events table, and not an event string to the users table.
You can create a migration or column definition with migration/model generators using the references type:
rails g model event name:string user:references
or
rails g migration add_user_id_to_event user:references
which will add column and the needed indexes.
Moreover, you have that a user has many events, so there is nothing like
user.event = Event.create
(there is no such method as User#event=) but instead
user.events << Event.create(...)