I'm looking to add a Favorite model to my User and Link models.
Business Logic
Users can have multiple links (that is, they can add multiple links)
Users can favorite multiple links (of their own or other users)
A Link can be favorited by multiple users but have one owner
I'm confused as to how to model this association and how would a user favorite be created once the models are in place?
class User < ActiveRecord::Base
has_many :links
has_many :favorites
end
class Link < ActiveRecord::Base
belongs_to :user
#can be favorited by multiple users
end
class Favorite < ActiveRecord::Base
belongs_to :user
belongs_to :link
end
How about the following data model:
class User < ActiveRecord::Base
has_many :links
has_many :favorites, :dependent => :destroy
has_many :favorite_links, :through => :favorites, :source => :link
end
class Link < ActiveRecord::Base
belongs_to :user
has_many :favorites, :dependent => :destroy
has_many :favorited, :through => :favorites, :source => :user
end
class Favorite < ActiveRecord::Base
belongs_to :user
belongs_to :link
end
Since User already has an association called links, and Link already has one called users, we cannot use the same name for the has_many :through association (e.g. User has_many :links, :through => :favorites would not work). So, we invent a new association name, and help Rails know what association to load from the intermediary association via the source attribute.
Here's some pseudocode for using this association:
# Some users
user1 = User.create :name => "User1"
user2 = User.create :name => "User2"
# They create some links
link1_1 = user1.links.create :url => "http://link1_1"
link1_2 = user1.links.create :url => "http://link1_2"
link2_1 = user2.links.create :url => "http://link2_1"
link2_2 = user2.links.create :url => "http://link2_2"
# User1 favorites User2's first link
user1.favorites.create :link => link2_1
# User2 favorites both of User1's links
user2.favorites.create :link => link1_1
user2.favorites.create :link => link1_2
user1.links => [link1_1, link1_2]
user1.favorite_links => [link2_1]
user2.links => [link2_1, link2_2]
user2.favorite_links => [link1_1, link1_2]
link1_1.favorited => [user2]
link2_1.destroy
user1.favorite_links => []
user2.links => [link2_2]
Related
I have this polymorphic association where a user can have many comments, a school can have many comments, and a comment can have many comments (or in my naming case replies):
class Comment < ActiveRecord::Base
attr_accessible :content
has_many :replies, :as => :commentable, :class_name => "Comment" # replies to comments
belongs_to :commentable, :polymorphic => true
belongs_to :commentor, :class_name => "User", :foreign_key => "user_id"
end
class User < ActiveRecord::Base
has_many :comments, :as => :commentable
has_many :commentors, # all users who commented on a user
:through => :comments,
:source => :commentor
end
class School < ActiveRecord::Base
has_many :comments, :as => :commentable
has_many :commentors, # all users who commented on a school
:through => :comments,
:source => :commentor
end
In the User, I can retrieve all who commented on a user using #user.commentors. Same goes for School, i.e. #school.commentors.
For the comments model, I would like to acheive the same thing for the Comments model where I can find all the commentors (or I guess repliers) to a comment; however, I have no idea what kind of association to create since a has_many :through association will not work like how it worked for the User and School model.
Use this:
has_many :reply_commentors, :through => :replies, :source => :commentor
I've got users and organisations with a join model UsersOrganisation. Users may be admins of Organisations - if so the is_admin boolean is true.
If I set the is_admin boolean by hand in the database, Organisations.admins works as I'd expect.
In the console, I can do Organisation.first.users << User.first and it creates an organisations_users entry as I'd expect.
However if I do Organisation.first.admins << User.last it creates a normal user, not an admin, ie the is_admin boolean on the join table is not set correctly.
Is there a good way of doing this other than creating entries in the join table directly?
class User < ActiveRecord::Base
has_many :organisations_users
has_many :organisations, :through => :organisations_users
end
class Organisation < ActiveRecord::Base
has_many :organisations_users
has_many :users, :through => :organisations_users
has_many :admins, :through => :organisations_users, :class_name => "User",
:source => :user,
:conditions => {:organisations_users => {:is_admin => true}}
end
class OrganisationsUser < ActiveRecord::Base
belongs_to :organisation
belongs_to :user
end
You can always override the << method of the association:
has_many :admins do
def <<(user)
user.is_admin = true
self << user
end
end
(Code has not been checked)
there are some twists with the has_many :through and the << operator. But you could overload it like in #Erez answer.
My approach to this is using scopes (I renamed OrganisationsUsers to Memberships):
class User < ActiveRecord::Base
has_many :memberships
has_many :organisations, :through => :memberships
end
class Organisation < ActiveRecord::Base
has_many :memberships
has_many :members, :through => :memberships, :class_name => 'User', :source => :user
# response to comment:
def admins
memberships.admin
end
end
class Memberships < ActiveRecord::Base
belongs_to :organisation
belongs_to :user
scope :admin, where(:is_admin => true)
end
Now I create new admins like this:
Organisation.first.memberships.admin.create(:user => User.first)
What I like about the scopes is that you define the "kind of memberships" in the membership class, and the organisation itself doesn't have to care about the kinds of memberships at all.
Update:
Now you can do
Organisation.first.admins.create(:user => User.first)
You can try below code for organization model.
class Organisation < ActiveRecord::Base
has_many :organisations_users
has_many :organisations_admins, :class_name => "OrganisationsUser", :conditions => { :is_admin => true }
has_many :users, :through => :organisations_users
has_many :admins, :through => :organisations_admins, :source => :user
end
From a person record I need to be able to add/display documents of specific types. Including the conditions for category_id works but at this point I can not assume that the category ids will remain the same as development progresses. This is also an issue with testing where I only create the categories I need.
Is there a way I can dynamically set the category_id, for example something like this:
has_many :personal_documents, :as => :documentable, :conditions => "category_id = #{DocumentCategory.find_by_name('Personal').id}", class_name: 'Document'
Models:
Person < AR::Base
has_many :documents, :as => :documentable
has_many :personal_documents, :as => :documentable, #:conditions => "category_id = 1"
has_many :legal_documents, :as => :documentable, #:conditions => "category_id = 2"
end
Animal < AR::Base
has_many :documents, :as => :documentable
end
Document < AR::Base
belongs_to :person
belongs_to :category
end
Could you simply use seeds with static ids?
I'm using Mongoid for my app and I have a problem setting up correct relationships for Users and subscriptions.
All I need to do is to make a simple "has one and belongs to one" relationship for UserSubscription model.
class User
has_many :user_subscriptions
end
class UserSubscription
belongs_to :user
has_one :user # user2 to which user1 is subscribed
field :category, :String
end
All I want to do is to have a list of subscriptions for each user:
> user1.user_subscriptions # list of subscription objects
> user1.user_subscriptions << UserSubscription.create(:user => user2, :category => 'Test')
> user1.user_subscriptions.where(:user => user2).delete_all
How to implement this? Thank you for help.
The problem is that you have two relations with the same name, and you need an inverse relation for your has_one :user relationship. You could always try something like this:
class User
include Mongoid::Document
has_many :subscriptions
has_many :subscribers, :class_name => "Subscription", :inverse_of => :subscriber
end
class Subscription
include Mongoid::Document
field :category
belongs_to :owner, :class_name => "User", :inverse_of => :subscriptions
belongs_to :subscriber, :class_name => "User", :inverse_of => :subscribers
end
Then you should be able to do things like:
> user1.create_subscription(:subscriber => user2, :category => "Test")
> user1.subscriptions.where(:subscriber => user2).delete_all
What is the recommended approach for finding multiple, unique associated models for a subset of another model? As an example, for a subset of users, determine unique artist models they have favorited.
One approach is to grab the users from the database, then iterate them all quering for favorites and building a unique array, but this seems rather inefficient and slow.
class User < ActiveRecord::Base
has_many :favorites
end
class Artist < ActiveRecord::Base
has_many :favorites
end
class Favorite < ActiveRecord::Base
belongs_to :user
belongs_to :artist
end
#users = User.find_by_age(26)
# then determine unique favorited artists for this subset of users.
The has_many association has a option called uniq for this requirement:
class User < ActiveRecord::Base
has_many :favorites
has_many :artists, :through => :favorites, :uniq => true
end
class Artist < ActiveRecord::Base
has_many :favorites
has_many :users, :through => :favorites, :uniq => true
end
class Favorite < ActiveRecord::Base
belongs_to :user
belongs_to :artist
end
Usage:
# if you are expecting an array of users, then use find_all instead of find_
#users = User.find_all_by_age(26, :include => :artists)
#users.each do |user|
user.artists # unique artists
end
Edit 1
I have updated the answer based on user's comment.
Solution 1- :group
Artist.all(:joins => :users, :group => :id,
:conditions => ["users.age = ?", 26])
Solution 2- SELECT DISTINCT
Artist.all(:joins => :users, :select => "DISTINCT artists.*",
:conditions => ["users.age = ?", 26]))