I'm trying to query on ActiveRecord multiple nested eager loaded associations with conditions like so:
user.books.includes(slot: [room: :school]).where("books.slot.room.school.id = 1")
Obviously this query is wrong, but basically what I'm trying to reach is a relation of user.books for a certain school.
My model structure is:
class User < ActiveRecord::Base
has_many :books
has_many :slots, through: :books
has_many :rooms, through: :slots
has_many :schools
end
class Book < ActiveRecord::Base
belongs_to :user
belongs_to :slot
end
class Slot < ActiveRecord::Base
has_many :books
belongs_to :room
end
class Room < ActiveRecord::Base
belongs_to :school
has_many :slots
end
class School < ActiveRecord::Base
has_many :users
has_many :rooms
has_many :slots, through: :rooms
has_many :books, through: :slots
end
Any ideas? Thanks in advance.
includes eager loads association records, while joins does what you want to do.
This question has been asked here numerous times. Please make sure that you look and try to find a similar question here before you ask one.
So you want to change your code like this:
user.books.joins(slot: [room: :school]).where(schools: { id: 1 })
Related
I made my first project and got into problem that I couldn't get the right category_information values for specific competitions category through relations. So I started thinking that this could be the wrong schema for this task, so my question - is it actually wrong?
Current Scheme:
Assuming the following relationships between models from your image.
class Competition < ApplicationRecord
has_many :categories
has_many :informations
has_many :category_informations, through: :categories
end
class Category < ApplicationRecord
belongs_to :competetion
has_many :category_informations
has_many :information, through: :category_informations
end
class CategoryInformation
belongs_to :catagory
belongs_to :information
end
class Information < ApplicationRecord
belongs_to :competetion
has_many :category_informations
has_many :catagory, through: :category_information
end
Model can relates with one_to_many_to_many using :through option
It explains a association used to set up a many-to-many connection with another model.
you can get the category_informations from competition like
Competition.first.category_informations
It is all for doing! Pretty good, right?
And you could do get information from category too
Category.first.informations
Actually wrong schema doesn't exist, just there exists some wrong association description.
You can get more usage to use association from docs at 2.3 section and 4.3 section
Assuming the following relationships between tables,
A competition has_many categories,
A competition has_many information,
A category has_many information,
A category has_many competition,
An information has_many category
You can use has_many_through relationships
class Category < ApplicationRecord
has_many :category_competitions
has_many :competitions, through: :category_competition
has_many :category_informations
has_many :informations, through: :category_informations
end
class Information < ApplicationRecord
has_many :category_informations
has_many :categories, through: :category_informations
end
class Competition < ApplicationRecord
has_many :category_competition
has_many :categories, through: :category_competitions
end
class CategoryCompetition < ApplicationRecord
belongs_to :category
belongs_to :information
end
class CategoryInformation < ApplicationRecord
belongs_to :category
belongs_to :information
end
By this way you can access,Categories of a particular competition by #competition.categories
This article might be helpful for you to understand associations better
https://www.sitepoint.com/master-many-to-many-associations-with-activerecord/
In my database there are 4 models
class MasterPayment < ActiveRecord::Base
has_many :payments
end
class Payment < ActiveRecord::Base
belongs_to :master_payment
belongs_to :payable, polymorphic: :true
end
class TreatmentPlan < ActiveRecord::Base
has_many :payments, as: :payable
end
class ArbitraryBillableItem < ActiveRecord::Base
has_many :payments, as: :payable
end
What i would like to do is set up an association in MasterPayment that will associate payables to master payments.
Currently, the closest i could find was setting up the master payment model as follows
class MasterPayment < ActiveRecord::Base
has_many :payments
has_many :treatment_plans, through: :payments, source: :payable, source_type: "TreatmentPlan"
has_many :arbitrary_billable_items, through: :payments, source: :payable, source_type: "ArbitraryBillableItem"
def payables
self.treatment_plans + self.arbitrary_billable_items
end
end
The only problem i have with this is that it doesn't feel like the "correct" way to do it.
The only reason i can see for rails not having a solution to this is because you would presumably have to union the tables to return it in one sql statement.
Is there an alternative way to accomplish this that will make more use of the active record associations?
This seems too simple but would it work?
def payables
self.payments.joins(:treatment_plans, :arbitrary_billable_items).distinct
end
Here is my models:
class User < ActiveRecord::Base
has_many :products
has_many :comments
end
class Product < ActiveRecord::Base
belongs_to :user
has_many :comments
end
class Comment < ActiveRecord::Base
belongs_to :user
belongs_to :product
end
I need to get comment records from current user products only
How do I do that? thanks
If we move the relationships to use a has_many: comments, through: products you can probably get what you're after:
class User < ActiveRecord::Base
has_many :products
has_many :comments, through: products
end
class Product < ActiveRecord::Base
belongs_to :user
has_many :comments
end
class Comment < ActiveRecord::Base
belongs_to :user
belongs_to :product
end
Now you can do user.comments.
The rails docs are here, which say:
A has_many :through association is often used to set up a many-to-many
connection with another model. This association indicates that the
declaring model can be matched with zero or more instances of another
model by proceeding through a third model. For example, consider a
medical practice where patients make appointments to see physicians.
I'm stuck in a circle of indecision and need a shove to break free. I'm a noob with Rails and I'm attempting to translate a pre-existing database using Rails conventions. Basically, I currently have 5 models/tables: Workorders, Mileage_logs, Time_logs, Parts, & Equipment. A Workorder can have many Mileage_logs, Time_logs, and Parts, because each of them is shown on the Workorder's index page. But, that's the seemingly easy part...
I'm getting confused when the Equipment model is introduced because it seems like it's basically the same thing as the Workorder.
What is the best way to handle this relationship setup? Is this an appropriate use for the has_many :through convention? Or, is this best done with simply having the workorder_id and equipment_id in the Mileage_log, Time_log, and Part models and then:
class Part < ActiveRecord::Base
belongs_to :workorder
belongs_to :equipment
end
class Mileage_log < ActiveRecord::Base
belongs_to :workorder
belongs_to :equipment
end
class Time_log < ActiveRecord::Base
belongs_to :workorder
belongs_to :equipment
end
class Workorder < ActiveRecord::Base
has_many :Time_logs
has_many :Parts
has_many :Mileage_logs
end
class Equipment < ActiveRecord::Base
has_many :Time_logs
has_many :Parts
has_many :Mileage_logs
end
Or, is the has_many through: relationship what I should look into for the Workorder & Equipment models?
class Workorder < ActiveRecord::Base
has_many :parts
has_many :mileage_logs
has_many :time_logs
end
class Equipment < ActiveRecord::Base
has_many :parts, through: :workorder
has_many :mileage_logs, through: :workorder
has_many :time_logs, through: :workorder
has_many :workorders
end
Any help would be greatly appreciated!
Also, any general advice on the route setup would be welcomed as well.
For some reason, my has_many through association isn't working. Here are my models:
class Interest < ActiveRecord::Base
has_many :evints
has_many :events, through: :evints
has_many :images, through: :events
end
class Event < ActiveRecord::Base
has_many :evints
has_many :images
has_many :interests, through: :evints
end
class Evint < ActiveRecord::Base
belongs_to :events
belongs_to :interests
end
The Evints table has three columns: interest_id, event_id, and id.
When I call #interest.events, I get the error message
uninitialized constant Interest::Events
Obviously, there's something going wrong with the association if #interest.events is being read as a constant!
Does anyone have any ideas?
Thanks!
Check your Evint class, it should be:
class Evint < ActiveRecord::Base
belongs_to :event
belongs_to :interest
end
On a different note, I think Evint isn't really a very good name. It'd suggest that you go with EventInterest, and name the table event_interests.