I'm trying to make a application where a user belongs to multiple courses and multiple assignments belong to a course. I'm using devise for the user model. I want to be able to find all the courses a user belongs to and all the assignments their courses have.
User model:
has_and_belongs_to_many :course
has_many :assignments, :through => :courses
Course model:
has_and_belongs_to :user
has_many :assignments
Assignment model:
belongs_to :course
this requires an intermediate table CoursesUsers with columns user_id and course_id
and column course_id in Assignment
with this give you can do things like
current_user.courses
current_user.assignments
some_course.assignments
some_course.users
(assuming there is a current_user or some_course)
Read about details here: Active Record Associations Especially how to setup the has_and_belongs_to_many association
Related
I'm setting up an app that has Users and Brands. Most users will not be associated with a brand, and will only be able to comment on Brand pages. Some users, however, will be associated with a single brand. I want these users to be the "admins" or owners of this brand. E.g. Users A and B are both "admins" of a brand, and so can create/edit/update the brand, etc. My question is, how should I set up the Brand resource such that it "belongs_to" multiple users? I understand that I could say brands have_many users, but is it weird to say that an object "has" a user? Is it more appropriate to "belong" to users? This description leads me to believe so: "For example, it makes more sense to say that a supplier owns an account than that an account owns a supplier."
It's definitely a has_many relationship.
But it may be clearer to refer to those special users as 'administrators' or 'admins'
class Brand
has_many :administrators, class_name: 'User'
end
If it turns out that a user can be administrator for several brands, then you'll need a join table, either HABTM or HMT. HMT is the better choice in case you want to store characteristics about the join (e.g. when he became administrator)
class BrandUser
belongs_to :user
belongs_to :brand
end
class Brand
has_many :brand_users
has_many :administrators, through: :brand_users, source: :user
end
class User
has_many :brand_users
has_many :brands, through: :brand_users
end
I am currently trying to create a system which allows for specific users to create a Course record which can be enrolled in by many other users. I've tried a few association techniques such as has_and_belong_to_many, has_many :through and number of other setups but have been unable to get it right.
Basically all that I need is the following:
Course belongs to (is created by) a single User (foreign_id => admin_id)
Course has many enrolled Users (Join Table?)
User has many created Courses
User can belong to many Courses
If you have any idea how this would be accomplished I would greatly appreciate your input.
I would use a Course model to represent the course information, with a user_id attribute to associate with the user who created the course. I would also make an association table/model called Enrollment which is an association between a User and a Course. You can then do something like this:
#User.rb
has_many :courses
has_many :enrollments
has_many :enrolled_courses, through: :enrollments, source: :course
#Enrollment.rb
belongs_to :course
belongs_to :user
#Course.rb
belongs_to :user
has_many :enrollments
has_many :users, through: :enrollment
With this configuration you can call course.user to receive the user who created the course, but you could also call course.users to receive the users who are enrolled in the course. On the opposite side, you can call user.enrolled_courses to receive the list of courses a user is enrolled in, or user.courses to receive a list of courses a user has created.
I'm trying to set up models in such a way that Users can create Lessons and then other users can sign up for them.
Right now my models are set up like this:
class Lesson < ApplicationRecord
belongs_to :teacher, class_name: 'User'
has_many :students, class_name: 'User'
end
class User < ApplicationRecord
has_many :lessons
has_many :students, :through => :lessons
end
I want to be able to access the users signed up for a lesson by #lesson.students for example. I'd also like to be able to get all the lessons that a student is participating in (can't really see how I'd do this with my current set up).
Are my model associations right for how I'd like to use them? If so, how can I create the migrations to add the necessary references to my database models?
If you want the ability to create nested resources from it's parents then you have to add:
accepts_nested_attributes_for
to the parent model.
Also, I recommend you to read how to set up has_many through relationships, you need a join model for rails to do its magic and link the 2 models
Once you set everything up, create the join model (with it's respective foreign keys, one for lesson and the other for user) rails will take care of the associations between the models, allowing you to do things like:
User.last.lessons #lessons created by the last user
and
Lesson.first.users #users subscribed to a lesson, in this case the first one
I have three models - Company, User and CompanyUser. The associations are as follows.
Company.rb
has_many :company_users
has_many :users, :through => :company_users
User.rb
has_many :company_users, :dependent => :destroy
belongs_to :company
CompanyUser.rb
belongs_to :company
belongs_to :user
For fetching current_user.company, what moddifications are to be made in the model association?
Any help would be appreciated.
It should be:
has_many :companies, through: :company_users
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.
So if you are creating three models and making a has_many :through association I believe that User will have many Companies and Company will have many Users.
But if you need that the user belongs to only one company instead of creating the third model save the company_id in the users table itself.
Update:
Now as your scenario is A company can have may users and User belongs to a single company, you need two models: User and Company. Your User model should have an attribute company_id and then company_id should be saved in users table only. Then the associations as follows:
class User < ActiveRecord::Base
belongs_to :company
end
class Company < ActiveRecord::Base
has_many :users
end
Then you can do current_user.company
You can get more information on associations in the RailsGuides
According to the associations you have taken,
user already have as association with the company through the Company User model, so user may have many companies according to your associations.
so,
class User < ActiveRecord::Base
has_many :company_users, :dependent => :destroy
has_many :companies, :through => :company_users
end
current_user.companies will give you the companies.
But if you need only one company for a user then,
class User < ActiveRecord::Base
belongs_to :company
end
take belongs_to company and save company_id in users table,
then you can call,
`current_user.company`
According to your logic,
I think you may need to create a new variable session current_company_user which is object CompanyUser.
And then, to fetch company by :
current_company_user.company
I'm in the process of trying to develop my first rails application and before I jump off into actually implementing my ideas, I was hoping I could get some help with my association planning.
My application is going to be an educational tool and I have some basic functionality that I need to implement. I want to have students that can register for and create courses. Within these courses, there will be one user who is the teacher and the rest are students. Within the course will be assignments that the teacher creates and that users are required to make a submission for. These are the basics. Eventually I want to add more functionality but as of now I just need the foundations set.
Here are my ideas so far on what the associations should look like:
class User < ActiveRecord::Base
has_many :enrollments
has_many :courses, :through => :enrollments
end
class Course < ActiveRecord::Base
has_many :enrollments
has_many :users, :through => :enrollments
end
class Enrollment < ActiveRecord::Base
belongs_to :user # foreign key - user_id
belongs_to :course # foreign key - course_id
end
However, I'm running into my wall of inexperience at the moment with how to appropriately handle the rest of the associations at this point. I could probably hack out something, but I'd prefer to do it as best as I can the first time.
How do I handle the associations related to assignments and submissions? Presumably a student's submission should belong_to them, but it is also specifically related to an assignment within the class. Assignments originate within a course, but are also closely tied to the user.
Finally, what's the best way to handle the relationships between a user and the class they create? A user creates a course. Does that course belong_to them? Should I just add a column to the course's table for storing the creator's id? Etc.
Thanks for the help.
Suggestion:
You might want to separate out your Teacher and Student models, since you're very likely to have different actions associated with each (and while they share some attributes, they really are different entities in your model, for example, you likely want just one teacher teaching in a course.)
You could derive both the Teacher model and the Student model from a User model that has the shared attributes and authentication.
Now to your questions:
If you'd like to keep the student that created the course associated, creator_id is the way I'd go. (If a teacher can create a course too, deriving Student and Teacher from a shared User model would help)
Assignments and Submissions:
You've pretty much defined it in words. Here is the code.
[If different students within a course could get different assignments, only then do you want to build a direct association between Student and Assignment, otherwise, use a through association]
class User < ActiveRecord::Base
has_many :enrollments
has_many :courses, :through => :enrollments
has_many :assignments, :through => :courses
has_many :submissions
end
class Course < ActiveRecord::Base
has_many :enrollments
has_many :users, :through => :enrollments
has_many :assignments
end
class Enrollment < ActiveRecord::Base
belongs_to :user # foreign key - user_id
belongs_to :course # foreign key - course_id
end
class Assignment < ActiveRecord::Base
belongs_to :course
has_many :submissions
end
class Submission < ActiveRecord::Base
belongs_to :assignment
belongs_to :user
end