I have a model A which belongs to my User model. I also have a model B, which belongs to my B model and also my User model (those are two different users, like doctor and patient). What I would like to do is some query like this:
B.joins(:user, {a: :user}).where("patient.name = 'some condition' or doctor.name='some other condition'")
The point here is: how can I specify that the users.name I'm querying is the one which is associated to A or B model?
Any help will be appreciated, thanks!
Perhaps something like this could work? (I haven't tested the code)
class User < ApplicationRecord
has_many :doctors
has_many :patients, through: :doctors
end
class Doctor < ApplicationRecord
belongs_to :user
has_many :patients
end
class Patient < ApplicationRecord
belongs_to :doctor
belongs_to :user
end
Patient.joins(user: {doctors: :user}).where("patient.name = 'some condition' or doctor.name='some other condition'")
Hope this helps!
You can create new classes named Patient and Doctor that inherit from User, then refer to users as patients and doctors instead of generic users.
class Doctor < User
has_many :a
end
class Patient < User
has_many :b
end
This is Single Table Inheritance:
https://api.rubyonrails.org/classes/ActiveRecord/Inheritance.html
Related
In my Ruby on Rails application I have invoices which can belong to either a person or a company. To make things even more complicated, a person can also belong to a company.
I figured that the right way to model this in Rails would be something like this:
class Invoice < ApplicationRecord
belongs_to :invoiceable, polymorphic: true
end
class Person < ApplicationRecord
has_many :invoices, as: :invoiceable
end
class Company < ApplicationRecord
has_many :invoices, as: :invoiceable
end
Is this the right way to do it?
And if so, can a person still belong to a company this way?
Thanks for any help.
I have Users and Trucks. I want the ability to say #truck.drivers << #users and #user.truck = #truck.
The solution is simple until I want the relationship to be stored in a join table.
# tables
:users
:id
:truck_drivers
:user_id
:truck_id
:truck
:id
I've gotten it to where I can say #truck.drivers << #user and #user.trucks << #truck, but I would like to limit a user to occupy one truck at a time, for my sanity.
Is it possible? A has_many/belongs_to with a join table? Or should I try a different approach? I'm not using a third model for the join table. It's just a table. Here's what I have so far.
class User < ApplicationRecord
has_and_belongs_to_many :trucks,
join_table: :truck_drivers, # points to the table
class_name: :Truck # looks for the truck model in the table
end
class Truck < ApplicationRecord
belongs_to :company
has_and_belongs_to_many :drivers,
join_table: :truck_drivers,
class_name: :User
end
The reason I need a join table in the first place is because each User can have many Roles: Admin, Manager, Driver, Customer Service, etc. I thought it didn't make sense to add a truck_id to all the users if all the users are not going to be using trucks.
It seems like you ought to be able to do something like:
#user.trucks << #truck unless #user.trucks.any?
Yes this is a standard strategy with rails using the :through keyword.
rails documentation: http://guides.rubyonrails.org/association_basics.html#the-has-many-through-association
Make a model called TruckUser with truck_id and user_id
then edit your classes:
class User < ApplicationRecord
has_many :truck_users
has_many :trucks, through: :truck_users
end
class Truck < ApplicationRecord
belongs_to :company
has_many :truck_users
has_many :drivers, through: :truck_users
end
class TruckUser < ApplicationRecord
belongs_to :truck
belongs_to :user
end
In my app I have 2 classes. User and Classroom. I use the user class as a student as well.
I'm trying to achieve a result where:
A classroom belongs to a user.
A user has many classrooms.
A classroom has one student through the user class.
A student can be associated to many classrooms.
To try and explain further. I have a classroom and the user is the creator of the classroom. When someone joins they are a student of the classroom and I only want there to be one student and one creator.
I want a student to be attached to lots of different classrooms and I want the classrooms to all belong to one user.
My current code for the two classes looks like this:
class User < ActiveRecord::Base
has_many :classrooms
end
class Classroom < ActiveRecord::Base
belongs_to :user
has_one :student, :class_name => "User"
end
Any advice is much appreciated. Thanks!
I think what you are trying to achieve is:
class User < ActiveRecord::Base
has_many :classroom_users
has_many :classrooms, through: :classroom_users
end
class ClassroomUser < ActiveRecord::Base
belongs_to :classroom
belongs_to :user
end
class Classroom < ActiveRecord::Base
has_many :classroom_users
has_many :users, through: :classroom_users
end
Sorry, this one is hard to phrase in the title. So here's what I'm trying to do. A workshop has many districts. Each district has exactly one district_contact (actually a district_contact_id). How can I use ActiveRecord to model the relationship between workshop and district_contact? I want to be able to do this:
Workshop.district_contacts
And get a collection of the actual user objects. Right now, I've done it using a short function:
def district_contacts
district_ids = []
self.districts.each do |district|
if district.contact_id
district_ids << district.contact_id
end
end
User.find(district_ids)
end
Define associations in the Workshop model:
has_many :districts
has_many :district_contacts, through: disctricts
Your model associations should look something like this.
class Workshop < ActiveRecord::Base
has_many :districts
has_many :district_contacts, through: disctricts
end
class District < ActiveRecord::Base
belongs_to :workshop
has_one :district_contract
end
I have a user model, farmer model, doctor model, and education model.
A farmer has a user and many educations.
A doctor has a user and many educations.
How do I setup the database for the education model?
Should it have a farmer_id AND a doctor_id?
But a education cannot belong to a farmer AND and doctor at the same time. It's one or the other.
So my education database entry would either have a farmer_id OR a doctor_id filled in, but not both.
Is there a way to guarantee that only one of the ids could be filled in at a time?
Or is there a better way to associate these models?
Your help would be appreciated!
Oh, and don't worry about the names of the models (farmer, doctor, etc.). It's just an example.
I see two possible solutions for this scenario.
The first one is to make use of polymorphic associations for education. That could look like this:
class Farmer < ActiveRecord::Base
belongs_to :user
has_many :educations, :as => :profession
end
class Doctor < ActiveRecord::Base
belongs_to :user
has_many :educations, :as => :profession
end
class Education < ActiveRecord::Base
belongs_to :profession, :polymorphic => true
end
So instead of education having a doctor_id or a farmer_id it has one profession_id and one profession_type.
The second solution would be to make use of Single Table Inheritance. And in your scenrio, that could be accomplished by letting a Doctor be a User instead of belonging to a User. And of course the same thing for a Farmer. That could look like this:
class User < ActiveRecord::Base
has_many :educations
end
class Farmer < User
end
class Doctor < User
end
class Education < ActiveRecord::Base
belongs_to :user
end
And in this scenario you would add a type column to the User model to store what type of class it is and then only having a user_id in the Education model
I think its appropriate to have the relations this way based on roles.
Class User
has_one :role
has_many :educations
end
Class Role
#What ever roles you have.
#Farmer or Doctor
belongs_to :user
end
class Education
belongs_to :user
end
This way you will store the user_id in the education object, which solves your problem.