I have a model Article and model User. In users, there will be one creator of the article and many readers. How do I link these together?
I was thinking:
class Article < ActiveRecord::Base
has_and_belongs_to_many :users
has_one created_by, through: :user (????)
end
class User < ActiveRecord::Base
has_many :articles
end
You can do like this
class Article < ActiveRecord::Base
has_and_belongs_to_many :users
has_one created_by_user,:class_name => 'User'
end
If you want to specify a custom foreign_key(which is useful in these cases),you can specify a foreign_key option
class Article < ActiveRecord::Base
has_and_belongs_to_many :users
has_one created_by_user,:class_name => 'User',:foreign_key =>'your_custom_fkey'
end
Related
I would like a user be able to create a course(so it should belong to one user) and also be able to join another course that it haven't created by him.What is the proper associations between the course and the user ? I want to make the following model associations:
Class User < ActiveRecord::Base
has_many :courses
has_many :comments ,through: :courses
end
Class Course < ActiveRecord::Base
has_and_belongs_to_many :users #here i am not sure
has_many :comments
end
Class Comment < ActiveRecord::Base
belongs_to :courses
end
I think what you should be able to do something like:
Class User < ActiveRecord::Base
has_many :courses
has_many :course_users
has_many :subscribed_courses, through: :course_users, source: :course # I think you should be able to do foreign_key: :course_id, class_name: 'Course'
has_many :comments ,through: :courses
end
Class Course < ActiveRecord::Base
belongs_to :user
has_many :course_users
has_many :participants, through: :course_users, source: :user # I think you should be able to do foreign_key: :user_id, class_name: 'User'
has_many :comments
end
Class Comment < ActiveRecord::Base
belongs_to :courses
end
#course_users is a join table for courses and users
class CourseUser < ActiveRecord::Base
# inside here you could have several other connections e.g grade of a user in a course within this join model
belongs_to :user
belongs_to :course
end
If I'm understanding what you're saying - you need to have a third model - you can call it enrollment
For Course you would use belongs_to :user if each course is created as a user.
Your Enrollment model with have two HABTAM
Class Enrollment < ActiveRecord::Base
has_and_belongs_to_many :users
has_and_belongs_to_many :courses
end
(An Aside, if a course is going to be offered more than once, you'll have to add an additional model for each instance of the course and the enrollment will belong to that model, and not courses)
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.
The Ruby on Rails app I am working on allows users to create and share agendas with other users.
In addition, we must be able to:
Display a list of agendas for each user, on his profile
Display a list of users associated with an agenda, on the agenda's page
When sharing an agenda with another user, define a role for this user, and display the role of this user on the list mentioned right above
I was going to go with a has_and_belongs_to_many association between the user and the agenda models, like that:
class User < ActiveRecord::Base
has_and_belongs_to_many :agendas
end
class Agenda < ActiveRecord::Base
has_and_belongs_to_many :users
end
But then I wondered whether this would let me get and display the #user.agenda.user.role list of roles on the given agenda page of a given user.
And I thought I should probably go with a has_many :through association instead, such as:
class User < ActiveRecord::Base
has_many :roles
has_many :agendas, through: :roles
end
class Role < ActiveRecord::Base
belongs_to :user
belongs_to :agenda
end
class Agenda < ActiveRecord::Base
has_many :roles
has_many :users, through: :roles
end
And although I was pretty comfortable about the idea of a user having several roles (one for each agenda), I am not sure about the idea of an agenda having several roles (one for each user?).
Finally, to add to the confusion, I read about the polymorphic association and thought it could also be a viable solution, if done this way for instance:
class Role < ActiveRecord::Base
belongs_to :definition, polymorphic: true
end
class User < ActiveRecord::Base
has_many :roles, as: :definition
end
class Agenda < ActiveRecord::Base
has_many :roles, as: :definition
end
Does any of the above solutions sound right for the situation?
UPDATE: Doing some research, I stumbled upon this article (from 2012) explaining that has_many :through was a "smarter" choice than has_and_belongs_to_many. In my case, I am still not sure about the fact that an agenda would have many roles.
UPDATE 2: As suggested in the comments by #engineersmnkyn, a way of solving this would be to go with two join tables. I tried to implement the following code:
class User < ActiveRecord::Base
has_many :agendas, through: :jointable
end
class Agenda < ActiveRecord::Base
end
class Role < ActiveRecord::Base
end
class Jointable < ActiveRecord::Base
belongs_to :user
belongs_to :agenda
has_many :agendaroles through :jointable2
end
class Jointable2 < ActiveRecord::Base
belongs_to :roles
belongs_to :useragenda
end
I am not sure about the syntax though. Am I on the right track? And how should I define the Agenda and the Role models?
UPDATE 3: What if I went with something like:
class User < ActiveRecord::Base
has_many :roles
has_many :agendas, through: :roles
end
class Role < ActiveRecord::Base
belongs_to :user
belongs_to :agenda
end
class Agenda < ActiveRecord::Base
has_many :roles
has_many :users, through: :roles
end
and then, in the migration file, go with something like:
class CreateRoles < ActiveRecord::Migration
def change
create_table :roles do |t|
t.belongs_to :user, index: true
t.belongs_to :agenda, index: true
t.string :privilege
t.timestamps
end
end
end
Would I be able to call #user.agenda.privilege to get the privilege ("role" of creator, editor or viewer) of a given user for a given agenda?
Conversely, would I be able to call #agenda.user.privilege ?
Okay I will preface by saying I have not tested this but I think one of these 2 choices should work well for you.
Also if these join tables will never need functionality besides a relationship then has_and_belongs_to_many would be fine and more concise.
Basic Rails rule of thumb:
If you need to work with the relationship model as its own entity, use has_many :through. Use has_and_belongs_to_many when working with legacy schemas or when you never work directly with the relationship itself.
First using your example (http://repl.it/tNS):
class User < ActiveRecord::Base
has_many :user_agendas
has_many :agendas, through: :user_agendas
has_many :user_agenda_roles, through: :user_agendas
has_many :roles, through: :user_agenda_roles
def agenda_roles(agenda)
roles.where(user_agenda_roles:{agenda:agenda})
end
end
class Agenda < ActiveRecord::Base
has_many :user_agendas
has_many :users, through: :user_agendas
has_many :user_agenda_roles, through: :user_agendas
has_many :roles, through: :user_agenda_roles
def user_roles(user)
roles.where(user_agenda_roles:{user: user})
end
end
class Role < ActiveRecord::Base
has_many :user_agenda_roles
end
class UserAgenda < ActiveRecord::Base
belongs_to :user
belongs_to :agenda
has_many :user_agenda_roles
has_many :roles, through: :user_agenda_roles
end
class UserAgendaRoles < ActiveRecord::Base
belongs_to :role
belongs_to :user_agenda
end
This uses a join table to hold the relationship of User <=> Agenda and then a table to join UserAgenda => Role.
The Second Option is to use a join table to hold the relationship of User <=> Agenda and another join table to handle the relationship of User <=> Agenda <=> Role. This option will take a bit more set up from a CRUD standpoint for things like validating if the user is a user for that Agenda but allows a little flexibility.
class User < ActiveRecord::Base
has_many :user_agendas
has_many :agendas, through: :user_agendas
has_many :user_agenda_roles
has_many :roles, through: :user_agenda_roles
def agenda_roles(agenda)
roles.where(user_agenda_roles:{agenda: agenda})
end
end
class Agenda < ActiveRecord::Base
has_many :user_agendas
has_many :users, through: :user_agendas
has_many :user_agenda_roles
has_many :roles, through: :user_agenda_roles
def user_roles(user)
roles.where(user_agenda_roles:{user: user})
end
end
class Role < ActiveRecord::Base
has_many :user_agenda_roles
end
class UserAgenda < ActiveRecord::Base
belongs_to :user
belongs_to :agenda
end
class UserAgendaRoles < ActiveRecord::Base
belongs_to :role
belongs_to :user
belongs_to :agenda
end
I know this is a long answer but I wanted to show you more than 1 way to solve the problem in this case. Hope it helps
I am implementing an authentication+authorization system in my Rails 3 Application.
I have a HABTM relationship with between Users and Roles.
The roles I will have are : manager,dealer,operator,admin
Now a manager can have many dealers under him. How do I model this relationship?
It is a simple question but I could not find an answer. Also a similar question here: Role-dependent associations but it does not clear things properly.
EDIT:
I am thinking my requirement is further simple. For me a user can only be either an Admin, Operator, Dealer or Manager.
For this I can simply add a role column to User table. How will the relationship between Managers and Dealers be enforced now?
I think you're looking for something more like
class Organization < ActiveRecord::Base
has_many :users
has_many :managers
has_many :dealer
has_many :admins
has_many :operators
has_many :dealer_users, :through => :managers, :class_name=>"User"
end
class Admin < ActiveRecord::Base
has_many :organizations
belongs_to :user
end
class Dealer
has_many :organizations
belongs_to :user
end
class Operator < ActiveRecord::Base
has_many :organizations
belongs_to :user
end
class Manager < ActiveRecord::Base
has_many :dealers
belongs_to :organization
end
class User < ActiveRecord::Base
has_many :organizations
has_many :admins
has_many :operators
has_many :managers
has_many :dealers
end
I have a model called company that has_many users then users belongs_to company.
class Company < ActiveRecord::Base
has_many :users
end
class User < ActiveRecord::Base
belongs_to :company
end
If something belongs to users will it also belong to company?
You have to use has_many :through association for this.
class Comment < ActiveRecord::Base
belongs_to :user
end
class User < ActiveRecord::Base
belongs_to :company
has_many :comments
end
class Company < ActiveRecord::Base
has_many :users
has_many :comments, :through => :users
end
Now you can do the following:
c = Company.first
c.users # returns users
c.comments # returns all the comments made by all the users in the company