i have the following models
class Airplane < ActiveRecord::Base
has_many :airtags
has_many :pictures, :through => :airtags
end
class Airtag < ActiveRecord::Base
attr_accessible :airable_type, :airable_id, :airplane_id
belongs_to :airplane
belongs_to :airable, :polymorphic => true
end
class Picture < ActiveRecord::Base
belongs_to :picturable, :polymorphic => true
has_many :airtags, :as => :airable, :dependent => :destroy
has_many :airplanes, :through => :airtags
end
in my airplane show, i want to list all pictures, ordered by their name.
#airplane.pictures.order(:name)
Related
I have the following models:
class User < ActiveRecord::Base
has_many :books, :dependent => :destroy
has_many :favorites
has_many :books, :through => :favorites
end
class Favorite < ActiveRecord::Base
belongs_to :book
belongs_to :user
validates :user_id, :book_id, :presence => true
end
class Book < ActiveRecord::Base
belongs_to :user
belongs_to :favorite
end
The idea is that a user can own a book and add a book from another user as favorite. In rails console, i tried User.find(1).favorites.books but got a NoMethodError: undefined method books'. Anduser.books` only returns the books owned by that user
Is there any way to retrieve all books that belong to a user's favorite in this case?
You are very close, but you shouldn't have two associations name books. Try something like this:
class User < ActiveRecord::Base
has_many :books, :dependent => :destroy
has_many :favorites
has_many :favorite_books, :through => :favorites, :source => :book
end
Then your query would simply be User.find(1).favorites_books
Models:
class Thread < ActiveRecord::Base
has_many :threaded, :through => :threaded, :foreign_key => :thread_id
class ThreadFeed < ActiveRecord::Base
belongs_to :threaded, :polymorphic => true
Model Fields
Thread (id)
ThreadFeed (id, thread_id, threaded_id, threaded_type)
Problem is with:
#thread.threaded
Rails is using (threaded_id, threaded_type) as the foreign key and I want thread_id to be the foreign key.
Take a look into this Railscast, Polymorphism
It will give you a better insight into how Polymorphism works.
First issue I notice is that it should be through :threadfeed, not :threaded
class Thread < ActiveRecord::Base
has_many :threadfeeds, :as => :threaded
In the Railscast, he has:
class Comment < ActiveRecord::Base
belongs_to :commentable, :polymorphic => true
end
class Article < ActiveRecord::Base
has_many :comments, :as => :commentable
end
class Photo < ActiveRecord::Base
has_many :comments, :as => :commentable
#...
end
class Event < ActiveRecord::Base
has_many :comments, :as => :commentable
end
The first problem is that Thread doesn't know what feed is:
class Thread < ActiveRecord::Base
has_many :feeds, :through => :thread_feeds, :as => :feeded
has_many :thread_feeds
class ThreadFeed < ActiveRecord::Base
belongs_to :feeded, :polymorphic => true
The second problem is the complexity of polymorphic. Here's a great article on it: http://blog.hasmanythrough.com/2006/4/3/polymorphic-through
Right now I have a rich many-to-many association with VideoVote as the independent record.
class VideoVote < ActiveRecord::Base
belongs_to :user
belongs_to :video
end
class User < ActiveRecord::Base
has_many :video_votes
has_many :voted_videos,
:through => :video_votes,
:source => :video
end
class Video < ActiveRecord::Base
has_many :video_votes
has_many :voted_users,
:through => :video_votes,
:source => :user
end
However, I want to trasform this into a polymorphic association where comments can also have many VideoVotes (I realize this is confusing, so I should probably change it to Votes). (also, a video will have many comments.) How should I do this?
You first want to add voteable_id:integer and voteable_type:string to your video_votes table.
Then your models will look like:
class VideoVote < ActiveRecord::Base
belongs_to :voteable, :polymorphic => true
end
class Comment < ActiveRecord::Base
has_many :video_votes, :as => :voteable
#code
end
class Video < ActiveRecord::Base
has_many :video_votes, :as => :voteable
#code
end
Then you can access them just like any other has_many:
#video.video_votes
#comment.video_votes
#etc.
I have a contact model, this includes name, address, phone number, etc.
I have a user model which should have_one contact.
I have a Customer model which has_many contacts.
I have a Producer model which has many contacts.
A contact can be only a user, a user and a customer, a user and a producer, or any combination of these three. I also need to be sure that the same contact record is linked when a contact is linked to multiple models for data integrity.
how should I create the associations?
This looks like a good application for a polymorphic association:
class User < ActiveRecord::Base
has_one :contact, :as => :contactable
end
class Customer < ActiveRecord::Base
has_many :contacts, :as => :contactable
end
class Producer < ActiveRecord::Base
has_many :contacts, :as => :contactable
end
class Contact < ActiveRecord::Base
belongs_to :contactable, :polymorphic => true
end
EDIT
It seems I didn't read the specs all the way through :) To associate the same contact with multiple Users, Customers, etc, you could use a has_many :through:
class User < ActiveRecord::Base
has_one :user_contact, :dependent => :destroy
has_one :contact, :through => :user_contact
end
class Customer < ActiveRecord::Base
has_many :customer_contacts, :dependent => :destroy
has_many :contacts, :through => :customer_contacts
end
class Producer < ActiveRecord::Base
has_many :producer_contacts, :dependent => :destroy
has_many :contacts, :through => :producer_contacts
end
class UserContact
belongs_to :user
belongs_to :contact
end
class CustomerContact
belongs_to :customer
belongs_to :contact
end
class ProducerContact
belongs_to :producer
belongs_to :contact
end
class Contact < ActiveRecord::Base
has_many :user_contacts, :dependent => :destroy # might use 'has_one' here depending on your requirements
has_many :users, :through => :user_contacts
has_many :customer_contacts, :dependent => :destroy
has_many :customers, :through => :customer_contacts
has_many :producer_contacts, :dependent => :destroy
has_many :producers, :through => :producer_contacts
end
That gives you one join table for each of the three associations. Each Contact can belong to none, one, or many of the three other models by adding rows to the join tables.
In my app I have the classes User, Video, and Vote. Users and Videos can relate to each other in two different ways: as a one-to-many or as a many-to-many. The former is when a User submits a Video (one user can submit many videos). The latter is when a user votes on a video (users have many videos through votes, and vice versa). Here is my code, which does not work (I think -- I may be doing something wrong in the view). Please help me understand the correct way to structure these associations:
class User < ActiveRecord::Base
has_many :videos, :as => :submissions
has_many :votes #have tried it without this
has_many :videos, :as => :likes, :through => :votes
end
class Vote < ActiveRecord::Base
belongs_to :video
belongs_to :user
end
class Video < ActiveRecord::Base
belongs_to :user
has_many :votes #have tried it without this . . . superfluous?
has_many :users, :as => :voters, :through => :votes
end
I haven't gone and checked, but it goes something like this:
Instead of
has_many :videos, :as => :likes, :through => :votes
Use
has_many :likes, :class_name => "Video", :through => :votes
Same with the bottom:
has_many :users, :as => :voters, :through => :votes
becomes
has_many :voters, :class_name => "User", :through => :votes
:as is used for polymorphic associations. See this chapter in docs for more info.
class User < ActiveRecord::Base
has_many :videos # Submitted videos
has_many :votes
has_many :voted_videos, :through => :votes # User may vote down a vid, so it's not right to call 'likes'
end
class Vote < ActiveRecord::Base
belongs_to :video
belongs_to :user
end
class Video < ActiveRecord::Base
belongs_to :user
has_many :votes
has_many :voters, :through => :votes
end
More details can be found here: http://guides.rubyonrails.org/association_basics.html
Hope it helps =)
Thanks for your help guys, definitely pointed me in the right direction. Here is the working code:
class User < ActiveRecord::Base
has_many :videos, :as => :submissions
has_many :votes
has_many :likes, :source => :video, :through => :votes
end
class Vote < ActiveRecord::Base
belongs_to :video
belongs_to :user
end
class Video < ActiveRecord::Base
belongs_to :user
has_many :votes
has_many :voters, :source => :user, :through => :votes
end
PS I kept it as :likes because in this app they won't be able to downvote, only upvote.