I have the following two models:
class Process < ActiveRecord::Base
has_many :activities, inverse_of: :artifact, dependent: :destroy
attr_accessible :name, :activities_attributes
def update_status!
if self.activities.all? {|a| a.completed? }
self.status = 'completed'
elsif self.activities.any? {|a| a.completed? }
self.status = 'in_progress'
else
self.status = 'not_started'
end
save!
end
end
class Activity < ActiveRecord::Base
belongs_to :process, inverse_of: :activities
attr_accessible :name,:completed_date
scope :completed, where("completed_date is not null")
end
Then in my Controller:
#activity = Activity.find(params[:id])
#activity.completed_date = Time.now
#activity.process.update_status!
If I put a debugger directly after this line, and print out #activity.completed it returns true, however #artifact.status is still "not_started" (assume no other activities).
However, if I add the following line before the update:
#activity.process.activities[#activity.process.activities.index(#activity)] = #activity
The status is updated correctly.
Why doesn't the change to #activity propagate into process.activities? And how can I make it propagate?
I don't this inverse_of works with has_many through. See this article: ActiveRecord :inverse_of does not work on has_many :through on the join model on create
Here is the relevant blurb from the RailsGuides:
There are a few limitations to inverse_of support:
They do not work with :through associations. They do not work with
:polymorphic associations. They do not work with :as associations. For
belongs_to associations, has_many inverse associations are ignored.
Related
I'm trying to get some records from table, but i don't know how to build this query.
I have some models.
class Request < ActiveRecord::Base
has_many :notifications, as: :source
has_many :decisions, dependent: :destroy
end
class Notification < ActiveRecord::Base
belongs_to :source, polymorphic: true
end
class Decision < ActiveRecord::Base
has_many :notifications, as: :source
belongs_to :request
end
So, I need to get all Notifications where source = some_request or source.request = some_request
Isn't it something simple as -
some_request.notifications
# or
some_decision.notifications
and if source is combination of request & decision then
notifications_ids = some_request.notifications.pluck(:id) +
some_decision.notifications.pluck(:id)
Notification.find(notifications_ids)
Your query should be Notification.where(source_id: some_request.id, source_type: 'Request')
Refer Active record association
Suppose I have a result from a query:
allCourses = Course.all
Then I also have another set:
myCourses = current_user.courses.all
How can I get a set of items that are in allCourses and NOT in myCourses?
Here are the models:
class Student < ActiveRecord::Base
has_many :student_enrollments, dependent: :destroy
has_many :courses, through: :student_enrollments
end
class Course < ActiveRecord::Base
has_many :student_enrollments, dependent: :destroy
has_many :students, through: :student_enrollments
end
class StudentEnrollment < ActiveRecord::Base
belongs_to :student
belongs_to :course
end
I can always write raw SQL script to achieve the result, but I prefer to find a Rails way to do it.
Thanks
Assume your fk is user_id.
ohterCourses = Course.where('user_id != ?', current_user.id)
I have a many to many relationship between two models as follows:
#users.rb
has_many :users_to_roles
has_many :roles, through: :users_to_roles
#users_to_roles.rb
belongs_to :user
belongs_to :role
#roles.rb
has_many :users_to_roles
has_many :users, through: :users_to_roles
I want to disable the deletion of roles if there are users who are "in this role". Here I have found two options who should do the work:
:restrict_with_exception causes an exception to be raised if there are
any associated records :restrict_with_error causes an error to be
added to the owner if there are any associated objects
but there is no example with the syntax of this and how it should work.
Could you help to make this valid:
#roles.rb
has_many :users_to_roles
has_many :users, through: :users_to_roles, dependent: restrict_with_exception
Such operations can be easily do using Callbacks. In my case, I have added the following method in my model:
# callbacks
before_destroy :check_for_users_in_this_role
def check_for_users_in_this_role
status = true
if self.security_users.count > 0
self.errors[:deletion_status] = 'Cannot delete security role with active users in it.'
status = false
else
self.errors[:deletion_status] = 'OK.'
end
status
end
Alternatively, you can rescue the exception in your controller. In this example, a contact may own interest, i.e.
class Interest < ActiveRecord::Base
belongs_to :contact
end
class Contact < ActiveRecord::Base
has_many :interests, :dependent => :restrict
end
Then in the controller:
def destroy
#contact = Contact.find(params[:id])
begin
#contact.destroy
rescue
flash[:msg] = "Can't delete - owns interest"
end
respond_to do |format|
format.html { redirect_to(:back) }
format.xml { head :ok }
end
end
The flash message will be displayed in the calling page.
The correct rails way is to do the following:
users.rb:
has_many :users_to_roles, dependant: :destroy # don't keep the join table entry if the user is gone
has_many :roles, through: :users_to_roles
Make sure that your join does not have redundant entries (in which either column is null or orphaned).
users_to_roles.rb:
belongs_to :user
belongs_to :role
# add validations presence of both user and role
# in both model and database.
Bonus, from rails 4.2 you can add forigen_key: true in your migration for referential integrity
Now in your role (I am assuming you name your models singularly and made a typo in the question), you add this:
role.rb:
has_many :users_to_roles, dependant: :restrict_with_error
has_many :users, through: :users_to_roles
I made it with my classes like this:
app/models/guest_chat_token.rb
class GuestChatToken < ApplicationRecord
has_many :chat_messages, as: :sendable, dependent: :restrict_with_exception
end
app/controllers/admin/application_controller.rb
class Admin::ApplicationController < ApplicationController
....
rescue_from ActiveRecord::DeleteRestrictionError do |exception|
redirect_to :back, notice:
"Be aware: #{exception.message}."
end
end
I am currently building very simple Comment system on Rails. The primary models are User, Albumpost, and Comment. Users can post Albumposts. For each Albumpost, Users can add Comments to the Albumpost. As a result, a Comment belongs to a User and belongs to an Albumpost.
The problem I'm having is that even with the proper associations in my models (see below), I can't get
#comment.user.name
when I'm trying to render the comments in the albumpost 'show' page (/views/albumposts/show.html.erb). When I go to the page, I can't get #comment.user.name (doesn't understand the association) and get a
"undefined method `name' for nil:NilClass"
Oddly I can get
#comment.albumpost.content
I've double-checked my models and also added the proper foreign keys to the models. Am I doing something wrong in the controllers?
Here are my models:
class Comment < ActiveRecord::Base
attr_accessible :body, :albumpost_id, :user_id
belongs_to :albumpost
belongs_to :user
end
class Albumpost < ActiveRecord::Base
attr_accessible :content
belongs_to :user
has_many :comments, dependent: :destroy
end
class User < ActiveRecord::Base
attr_accessible :name, :email, :password, :password_confirmation
has_many :albumposts, dependent: :destroy
has_many :comments, dependent: :destroy
end
Here are the relevant parts of my Albumpost and Comments controllers:
class AlbumpostsController < ApplicationController
def show
#albumpost = Albumpost.find(params[:id])
#comments = #albumpost.comments
#comment = Comment.new
#comment.albumpost_id = #albumpost.id
#comment.user_id = current_user.id
end
end
class CommentsController < ApplicationController
def create
albumpost_id = params[:comment].delete(:albumpost_id)
#comment = Comment.new(params[:comment])
#comment.albumpost_id = albumpost_id
#comment.user_id = current_user.id
#comment.save
redirect_to albumpost_path(#comment.albumpost)
end
end
I think you should prefer setting objects to relations instead of setting their ids. For example, you should do this:
#comment.user = current_user
instead of
#comment.user_id = current_user.id
ActiveRecord will take care of setting corresponding *_id fields. I'm not sure how it handles the reverse. (it should autoload though, if I understand correctly)
My models look like this:
class Movie < ActiveRecord::Base
attr_accessible :title, :year, :rotten_id, :audience_score,
:critics_score, :runtime, :synopsis, :link, :image
has_many :jobs, :dependent => :destroy
has_many :actors, :through => :jobs
end
class Actor < ActiveRecord::Base
attr_accessible :name
has_many :movies, :through => :jobs
has_many :jobs, :dependent => :destroy
end
class Job < ActiveRecord::Base
attr_accessible :movie_id, :actor_id
belongs_to :movie
belongs_to :actor
end
When I'm displaying my index of Actors, I'd like to show the number of movies each actor has starred in. I can do this with #actor.movies.count, however this generates an SQL query for each actor. With, say, 30 actors, this will result in 30 extra queries in addition to the initial.
Is there any way to include the count of movies each actor has participated in, in the initial Actor.all call? And thereby getting things done with only one call. Extra bonus if this was sorted by said count.
Update:
All answers provided has been helpful, and though it turned into some dirt-slinging-contest at some point, it worked out well. I did a mish-mash of all your suggestions. I added a movies_counter column to my Actor model. In my Job model I added belongs_to :actor, :counter_cache => :movies_counter. This works brilliantly, and is automatically updated when i create or destroy a movie, without me adding any further code.
As #Sam noticed, you should add new column to actors table movies_counter
rails g migration add_movies_counter_to_actor movies_counter:integer
Now you can edit your migration
class AddMoviesCounterToActor < ActiveRecord::Migration
def self.up
add_column :actors, :movies_counter, :integer, :default => 0
Actor.reset_column_information
Actor.all.each do |a|
a.update_attribute :movies_counter, a.movies.count
end
end
def self.down
remove_column :actors, :movies_counter
end
end
And run it
rake db:migrate
Then you should add two callbacks: after_save and after_destroy
class Movie < ActiveRecord::Base
attr_accessible :title, :year, :rotten_id, :audience_score,
:critics_score, :runtime, :synopsis, :link, :image
has_many :jobs, :dependent => :destroy
has_many :actors, :through => :jobs
after_save :update_movie_counter
after_destroy :update_movie_counter
private
def update_movie_counter
self.actors.each do |actor|
actor.update_attribute(:movie_count, actor.movies.count)
end
end
end
Then you can call some_actor.movies_counter
Add a column to your Actor table called 'movie_count'. Then add a call back in your Actor model that updates that column.
class Movie < ActiveRecord::Base
has_many :actors, :through => :jobs
before_save :update_movie_count
def update_movie_count
self.actor.update_attribute(:movie_count, self.movies.size)
end
end
That way your just have an integer that gets updated instead of calling all records.