has_and_belongs_to_many relationship in ruby on rails - ruby-on-rails

Question

I am trying to make a website for a tennis coach using ruby on rails. I am completely new to this and I am struggling with some of the terminology. The website has a login system where users can sign in and then sign up for different events that the tennis coach has created. So basically the users can go to many events and the events can have many users attending. I have made a has_and_belongs_to_many relationship between my users table and events table and the code is below:
Here is my migration:
class CreateEventsUsers < ActiveRecord::Migration
def change
create_table :events_users, :id => false do |t|
t.integer :event_id
t.integer :user_id
end
add_index :events_users, :event_id
add_index :events_users, :user_id
add_index :events_users, [:event_id, :user_id]
end
def self.down
drop_table :events_users
end
end
Here are my models:
class User < ActiveRecord::Base
has_and_belongs_to_many :events
end
class Event < ActiveRecord::Base
has_and_belongs_to_many :users
end
Here is my event form:
<li>
<%= link_to event.title, event %>
| <%= link_to "delete", event, method: :delete %>
| *insert sign up here*
</li>
Basically my question is, how would I make a form and a controller that would let a signed in user, sign up for one of the events in the database? I have been stuck on this for days. Any help would be greatly appreciated.

Answer 1

I would suggest using a has_many through instead of using has_and_belongs_to for scalability issues and is a suggested practice. Coming to your requirement, I did a similar thing but with users following other users and tried to adopt some of them for your requirement.
class Event < ActiveRecord::Base
has_many : Relationship
has_many : users, :through => :Relationships
end
class User < ActiveRecord::Base
has_many :Relationship
has_many :events, :through => :Relationships
//define other methods//
def follow!(event_id)
relationships.create!(event_id: event.id)
end
end
class Relationship < ActiveRecord::Base
attr_accessible :event_id
belongs_to :events
belongs_to :users
end
You need to create the relationship migration like this
class CreateRelationships < ActiveRecord::Migration
def change
create_table :relationships do |t|
t.integer :user_id
t.integer :event_id
t.timestamps
end
add_index :relationships, :user_id
add_index :relationships, :event_id
add_index :relationships, [:user_id, :event_id], unique: true
end
end
You can try adding a button on the events page view like this.
<%= form_for(current_user.relationships.build(evnt_id: #user.id)) do |f| %>
<div><%= f.hidden_field :event_id %></div>
<%= f.submit "Follow", class: "btn btn-large btn-primary" %>
<% end %>
Relationship controller can be something like this.
class RelationshipsController < ApplicationController
def create
#user = User.find(params[:relationship][:event_id])
current_user.follow!(#user)
respond_to do |format|
format.html { redirect_to #user }
end
end
end
This tutorial was very helpful for me in developing the application for users to follow other users. Hope it will help you too. Good luck !!
http://ruby.railstutorial.org/chapters/following-users#top

Answer 2

If you haven't discovered it already, you are in for a real treat if you checkout railscasts from Ryan Bates. Here is a tutorial on using checkboxes in a form with a HABTM association--actually he suggests, and you should consider it, moving to has_many, through relationship instead of HABTM.
Regardless, it should at least give you an idea of how you can make it work in your app. http://railscasts.com/episodes/17-habtm-checkboxes-revised. That episode may require a membership, however, the $9 bux/month is totally reasonable for what you're getting.