I have a "two middleman" model setup as shown below:
User
has_many :comments
has_many :ratings
Comment
belongs_to :user
belongs_to :movie
Rating
belongs_to :user
belongs_to :movie
Movie
has_many :comments
has_many :ratings
Whats the best way to get all Movies that a User is associated with (either commented on or rated)?
I'd like to be able to call User.get_movies(user_id) and get back an ActiveRecord::Relation object so that it's chainable (i.e. User.get_movies(user_id).limit(3).order(...)). This returns a regular old array, and I suspect I'm hitting the database way more than I need to be.
def self.get_movies(user_id)
user = self.where(:id => user_id).includes({:comments => :movie}, {:ratings => :movie})
movies = []
user.comments.each do |comment|
movies.push(comment.movie)
end
user.ratings.each do |rating|
movies.push(rating.movie)
end
movies.uniq!
end
def movies
Movie.includes(:ratings, :comments).where("`ratings`.user_id = ? OR `comments`.user_id = ?", self.id, self.id)
end
Untested, but I'm pretty sure using a joins instead of includes also works.
Related
I am designing a database of woodwind instrument sounds, and would like to create a table that joins pairs of sounds that a performer can combine into, for example, a trill. Such relations are transitive: if sound A has a 'Sound Relation' with sound B, then sound B has that same 'Sound Relation' with sound A.
I am familiar with join tables, but I've never seen them used to join 'like' objects, only to join 'unlike' objects, such as tags and posts, so I'm wary of going that direction.
I realize the example below looks extremely dubious, but it gives an idea of what I'm after. What is a better way of doing it? (Using ActiveRecord syntax)
Models
class Sound < ActiveRecord::Base
has_many :linked_sounds, through: :sound_relations, class_name: "Sound", foreign_key: ???
end
class Sound_Relation < ActiveRecord::Base
has_many :sounds
end
Migration
class CreateSoundRelations < ActiveRecord::Migration
def change
create_table :sound_relations do |t|
t.integer first_sound_id # This cannot possibly be right.
t.integer second_sound_id # Surely the transitivity of the
# relationship should be more evident?
end
end
end
You might try something like:
class Set < ActiveRecord::Base
has_many :sound_sets
has_many :sounds, :through => :sound_sets
end
class SoundSet < ActiveRecord::Base
belongs_to :sound
belongs_to :set
end
class Sound < ActiveRecord::Base
has_many :sound_sets
has_many :sets , :through => :sound_sets
has_many :set_sound_sets, :through => :sets , :source => :sound_sets
has_many :set_sounds , :through => :set_sound_sets, :source => :sound
end
So, no more "sound_1" and "sound_2" ... they are both just sounds. For every sound you can also use the set_sounds method to retrieve all of the sounds associated with it.
This would also allow more than two sounds in a relation, and you might like to put a "type" on the sets model.
Edit: If you look at the query generated, you'll find that sound_sets is mentioned in there twice, once with a different alias. The key to eliminating "self" joins is to include a clause in the association along the lines of:
has_many :set_sounds ,
{where("sound_sets.sound_id != set_sound_sets_sound_set_sounds.sound_id")},
:through => :set_sound_sets,
:source => :sound
... where "sound_set_sounds" is the table alias. If you can post the query in the comments I can update this with the actual alias.
I am trying to retrieve a list of all tasks, where each task has a developer and reviewer. I am able to retrieve the list but it contains developer_id and reviewer_id. How do I retrieve a list containing developer name and retriever name?
class Person < ActiveRecord::Base
end
class Unread_Object < ActiveRecord::Base
belongs_to :person
end
class Developer < Person
has_many :tasks
end
class Reviewer < Person
has_many :tasks
has_many :unread_objects
end
class Task < ActiveRecord::Base
belongs_to :developer
belongs_to :reviewer
has_many :documents
after_save :add_task_to_unread_objects
protected
def add_task_to_unread_objects
Person.find_each do |person|
Unread_Object.create(
:person_id => person.id,
:internal_object_id => self.internal_object_id,
:unread_cause => 'Create')
end
end
end
Things I have tried.
get '/taskslist' do
#Task.includes([:developer, :reviewer]).all.to_json
#Task.joins(:developer,:reviewer).select("tasks.*, people.*").to_json #works somewhat but only shows one name
#Task.includes(:reviewer.name,:developer.name).all.to_json #"undefined method `name' for :reviewer:Symbol"
#Task.find(:all, :include => {:people => :name}).to_json #Couldn't find all Tasks with 'id': (all, {:include=>{:people=>:name}})
end
I hope to get Tasks json with nested json for developer, reviewer and other objects.
This question is follow up of this.
After some searching found as_json(include: <association>)
So this works
Task.includes(:developer,:reviewer).all.as_json(include: [:developer,:reviewer]).to_json
But other alternatives need to be seen.
Models:
A User has_one Ucellar
A Ucellar belongs_to User
I have confirmed from multiple sources that these are set up correctly. For posterity, here is the top portion of those two models.
class User < ActiveRecord::Base
has_many :authorizations
has_one :ucellar
validates :name, :email, :presence => true
This is actually the entire Ucellar model.
class Ucellar < ActiveRecord::Base
belongs_to :user
end
Ucellar has a column called user_id, which I know is necessary. The part of my application that creates a user uses the method create_with_oath. Below is the entire User class. Note the second line of the create method.
class User < ActiveRecord::Base
has_many :authorizations
has_one :ucellar
validates :name, :email, :presence => true
def create
#user = User.new(user_params)
#ucellar = #user.create_ucellar
end
def add_provider(auth_hash)
# Check if the provider already exists, so we don't add it twice unless authorizations.find_by_provider_and_uid(auth_hash["provider"], auth_hash["uid"])
Authorization.create :user => self, :provider => auth_hash["provider"], :uid => auth_hash["uid"]
end
end
def self.create_with_omniauth(auth)
user = User.create({:name => auth["info"]["name"], :email => auth["info"]["email"]})
end
private
def user_params
params.require(:user).permit(:name, :email)
end
end
EDIT:
Forgot to summarize the symptoms. On create, the user is in the db, with no exceptions thrown, and nothing to signify that anything went wrong. However, the related ucellar is never created. Per the documentation Here, the create method should create AND save the related ucellar.
It should create ucellar too.
Try to get the error messages after the creation by calling:
raise #user.errors.full_messages.to_sentence.inspect
I'm not sure why this wasn't working, but I ended up just moving this code out of the create action of the user controller, and putting it directly after an action that was creating a user. It solved my issue though. Thanks everyone for your help!
I have the following association code in my user.rb model file
class User < ActiveRecord::Base
has_many :sent_messages, class_name: 'ChatMessage', foreign_key: 'sender_id'
has_many :received_messages, class_name: 'ChatMessage', foreign_key: 'receiver_id'
end
I want a method in the ChatMessage model which should be triggered by the following
current_user.sent_messages
current_user.received_messages
The method should return the name of the association that was called.
Eg:
class ChatMessage < ActiveRecord::Base
after_find :get_association_name
def get_association_name
self.association_name // this should return sent_message or received_message depending on whether current_user.sent_messages or current_user.received_messages was called
end
end
Is there a way to get this association name in rails?
Any help is much appreciated. Thanks
I am not sure, exactly what you are looking for, but
CurrentUser.reflect_on_all_associations(:has_many)
will give an array of all has_many associations.
I haven't used AR associations extensions for cases like this, but you should be able to do:
has_many :sent_messages, class_name: 'ChatMessage', foreign_key: 'sender_id' do
def get_association_name; 'sent_messages'; end
# or, to make this more generic,
# def get_association_name; proxy_association.reflection.name.to_s; end
end
And the method should be accessible from your relation. If you were using Rails 4, you could extract the generic version out into a separate module to extend your associations more succinctly. See http://guides.rubyonrails.org/association_basics.html#association-extensions.
EDIT
Try:
has_many :sent_messages, class_name: 'ChatMessage', foreign_key: 'sender_id' do
def and_set_type
proxy_association.target.each do |msg|
msg.update_attribute(:type, 'sent')
end
scoped
end
end
And then access your sent_messages with current_user.sent_messages.and_set_type.
I'm trying to figure out the best way to setup my database and models for the following scenario.
A user can like an infinite number of songs.
A song can be liked once by an infinite number of users.
I have these tables:
songs, users, likes etc... Following RoR conventions.
The table named likes has these foreign keys: user_id, song_id. And also a field named 'time' to save a timestamp when the song was liked.
I'm not sure of how to do this, I would like to be able to use code like this in my controllers:
User.find(1).likes.all
This should not return from the likes table, but join the songs table and output all the songs that the user likes.
What are the best practises to achieve this in Ruby on Rails following their conventions?
Unless you need to act specifically on the likes table data, the model itself is probably not necessary. The relationship is easy:
class User < ActiveRecord::Base
has_and_belongs_to_many :songs
end
class Song < ActiveRecord::Base
has_and_belongs_to_many :users
end
This will join through the currently non-existent song_users table. But since you want it to join through likes you can change each one to this:
has_and_belongs_to_many :songs, :join_table => 'likes'
If you want to be able to call User.find(1).likes and get songs, then change the user's version to this:
class User < ActiveRecord::Base
has_and_belongs_to_many :likes, :join_table => 'likes', :class_name => 'Song'
end
And you could change the songs version to something like this:
class Song < ActiveRecord::Base
has_and_belongs_to_many :liked_by, :join_table => 'likes', :class_name => 'User'
end
This will give you Song.find(1).liked_by.all and give you the users (You could keep it to users if you wanted using the first version)
More details on habtm relationships can be found here: http://apidock.com/rails/ActiveRecord/Associations/ClassMethods/has_and_belongs_to_many
Edit to add
If you want to act on the join table for whatever reason (you find yourself needing methods specifically on the join), you can include the model by doing it this way:
class User < ActiveRecord::Base
has_many :songs, :through => :likes
has_many :likes
end
class Like < ActiveRecord::Base
belongs_to :user
belongs_to :song
end
class Song < ActiveRecord::Base
has_many :users, :through => :likes
has_many :likes
end
This will let you do User.find(1).songs.all, but User.find(1).likes.all will give you the join data