class Campaign < ActiveRecord::Base
has_many :posts
has_many :users
end
class Post < ActiveRecord::Base
has_and_belongs_to_many :users
belongs_to :campaign
end
class User < ActiveRecord::Base
has_and_belongs_to_many :posts, :join_table => "users_posts"
belongs_to :campaign
end
If user saw this post I add him to post.users. I need find first unwatched post of user campaign. Smth like this:
current_user.campaign.posts.where('posts.users not include current_user')
MrYoshiji, Thanks a lot! You remember me about include. Before I tried join and it did not work with nil because INNER JOIN, I solved my problem with instance method:
def unwatched_post
campaign.posts.includes(:users).where('users.id != ? OR users.id IS NULL', self.id).first
end
Related
I've 3 models in Rails 5:
Product
class Product < ApplicationRecord
belongs_to :category
has_and_belongs_to_many :stores
end
Store
class Store < ApplicationRecord
has_many :admin_users
has_and_belongs_to_many :roles
has_and_belongs_to_many :products
end
ProductsStores
class ProductsStores < ApplicationRecord
self.primary_key = :store_id
end
When I try to delete one record of the join table ProductsStores with the command ProductsStores.first.destroy all records in the join table are destroyed. Why?
Could anyone help me?
Thank you in advance!
At first, you have to understand differences between HABTM and has_many through:
http://guides.rubyonrails.org/association_basics.html#the-has-and-belongs-to-many-association
If you created linkedin model and wanna using this model, you have to use has_many through: association, and add to this model belongs_to :product and belongs_to :store. Then with flag dependent: :destroy you will can destroy or not destroy linked models as default.
I'm trying to querying on polymorphic associations in Rail, and come across with this problem. I have a few models, User, MorningVisit, AfternoonVisit, NightVisit, and Result
class User < ActiveRecord::Base
attr_accessible :name
has_one :morning_visit
has_one :afternoon_visit
has_one :night_visit
end
class MorningVisit < ActiveRecord::Base
belongs_to :user
has_many :results, as: :visitable
end
class AfternoonVisit < ActiveRecord::Base
belongs_to :user
has_many :results, as: :visitable
end
class NightVisit < ActiveRecord::Base
belongs_to :user
has_many :results, as: :visitable
end
class Result < ActiveRecord::Base
attr_accessible :type
belongs_to :visitable, polymorphic: true
end
Everything stores perfectly, but now I need to do some search and querying on User using filterrific.
If I do
includes(:visitable => :user).order("user.name")
I get
Can not eagerly load the polymorphic association :visitable
So I tried to manually joined MorningVisit with
.joins( "JOIN morning_visits ON lab_results.visitable_id = morning_visit.id AND lab_results.visitable_type = 'MorningVisit'")
.joins( "INNER JOIN `users` ON `morning_visits`.`user_id` = `users`.`id` ")
And order("user.name") works.
But if I added
.joins( "JOIN afternoon_visits ON lab_results.visitable_id = afternoon_visits.id AND lab_results.visitable_type = 'AfternoonVisit'")
It returns nothing. And if I tried outer join, it keep telling me my SQL syntax was wrong.
Does anyone have a solution for this?
I have three models, Subrating, Thing, and Category. Subrating belongs_to Thing, and Thing has_many Categories.
I have a list of Subratings, and I'm trying to eager-load the Categories that are associated with the Things that are associated with each Subrating.
This is what I tried:
controller
#subratings = Subrating.all( :include => { :thing => :categories })
view
<% #subratings.sort_by(&:rating).reverse.each do |subrating| %>
<%= subrating.thing.categories.sort_by(&:thing_count).second.name %>
<% end %>
But it doesn't solve my n+1 problem. I'm not even sure whether the database is lazy-loading Things or Categories or both, but this is the line that keeps reappearing hundreds of times in my server:
CACHE (0.0ms) SELECT COUNT(*) FROM "things" INNER JOIN "category_things" ON "things"."id" = "category_things"."thing_id" WHERE "category_things"."category_id" = $1 [["category_id", 1]]
What am I doing wrong?
associations
class Subrating < ActiveRecord::Base
belongs_to :thing
end
class Thing < ActiveRecord::Base
has_many :category_things
has_many :categories, :through => :category_things
has_many :subratings
end
class Category < ActiveRecord::Base
has_many :category_things
has_many :things, :through => :category_things
end
class CategoryThing < ActiveRecord::Base
belongs_to :category
belongs_to :thing
end
Maybe you should try to call includes on the Model class like:
#subratings = Subrating.includes(thing: [:categories])
as documented in http://apidock.com/rails/ActiveRecord/QueryMethods/includes
although it also should work the way you are trying it, since .all is an alias for .find(:all) but then i would propose to try:
#subratings = Subrating.all( :includes => { :thing => [:categories] })
(note that i changed include to includes and made thing point to an array)
#subratings = Subrating.includes(:thing => :categories)
This will also work for you and give you all records of substrings table.
I have two models lets suppose
class A < ActiveRecord::Base
has_many :bs
end
class B < ActiveRecord::Base
belogns_to :a
end
now because of some system changes I need to convert this association to many to many some thing like this
class A < ActiveRecord::Base
has_and_belongs_to_many :bs
end
class B < ActiveRecord::Base
has_and_belongs_to_many :as
end
OR
class A < ActiveRecord::Base
has_many :cs
has_many :bs, through: :cs
end
class B < ActiveRecord::Base
has_many :cs
has_many :as, through: :cs
end
class C < ActiveRecord::Base
belongs_to :a
belongs_to :b
end
what is best way to do this and most importantly I DO NOT WANT TO LOSE MY EXISTING DATA. Existing records should automatically adopt these changes. Thanks in advance.
many to many means you have connected table(model) between two other, so you could just create this one and write relation to it, after that you could remove garbage ids from B.
A, B are not good names;)
imagine you have User and Comments, and you decide that comments can have also many users, so it can look like:
class User
has_many :comments # will be changed
has_many :user_comments
end
class UserComments
belong_to :user
belong_to :comment
end
class Comment
belong_to :user # id will be removed from table and relation will be changed
has_many :user_comments
end
# as direction for import could be something like:
User.all.each do |user|
user.comments.each do |comment|
UserComments.create user: user, comment: comment
end
end
Everyday, I need to run the a script and send all of my users an 'exam' or set of questions. I have modelled as class 'Exam' which subclasses ActiveRecord::Base. Now, how do I send user's instances of Exam?
What I was thinking was create a new class called 'ExamInstance' which would have a reference to 'Exam' and the user.
I am new to SQL and ActiveRecord so if someone can help me better model this so I can avoid problems later on or just give me some insight, that would be great.
Thanks
I'll suggest just use has_many :through create a model UserExam for many to many relation between exam and user
class User < ActiveRecord::Base
has_many :users_exams
has_many :exams, :through => :users_exams
end
class UserExam < ActiveRecord::Base
belongs_to :users
belongs_to :exams
end
class Exam < ActiveRecord::Base
has_many :users_exams
has_many :users, :through => :users_exams
end
For more information on has_many :through
Add 'ExamUser' model to keep track of exam and the corresponding users references. The model skeleton will look something like:
class ExamUser < ActiveRecord::Base
belongs_to :exam
belongs_to :user
end
You could then loop through the records of this table to send your questions.
You can design your new model like this..
class ExamUser < ActiveRecord::Base
belongs_to :user # user has many exams
belongs_to :exam # exam has many users
end