Model help with school app

Rails
1

Hello. I have an app that I need help laying out the model
relationships for.

Schools can have more than one admin
Schools can have more than one student
Students can only belong to one school
BUT Admins can have many schools

Students and Admins are both Users, just with different Roles

So, I have a Users model and a Roles model

Users can be either have a student role or an admin role

How do I relate the models so that a school can have many users
but a student can only have one school while an admin can have many
schools?

I appreciate your help.

2

So, I have a Users model and a Roles model

I’m lost now. Why would you separate Users and Roles, unless some admins
are
also students?

I would have Schools, Admins, and Students models, unless admins and
students somehow need the same functionality.

3

Because the Users model controls my login’s. At least that’s what I’ve
been thinking.

So, a user comes to my page, logs in and based on their role, either
student or admin, are given different permissions.

b/c students need to see their courses, assignments and grades, but
not edit them.

I’ve been wondering whether or not to keep one Users table, i just
think it makes things cleaner?

I am open to thoughts on that.

4

instead of roles you can use STI (single table inheritance) where you
have one table and one model, but then the model gets extended with
other classes:

class User < AR::Base
has_many :memberships
end

class Student < User
has_one :school, :through => :memberships
end

class Admin < user
has_many :schools, :through => :memberships
end

Now, Admin and Student are both Users, but Student has the methods
schools, school= …etc, whistl admins have schools, schools<<… etc.

Your table users will need a column called type which is a string and
you will never actually use it explicitely, so just put it there and
forget about it.

obviously:
Student.all #=> an array of only students
Admin.all #=> an array of only admins
User.all #=> an array of all users: User + Students + Admins

5

This is a very common scenario that comes up all the time. The problem
is that there isn’t a “silver bullet” solution for this. Different
applications often end up with different needs.

Here are some of the solutions I’ve used in the past for various
applications:

  1. Single-table Inheritance (STI)
    This can be a robust solution that covers a large number of
    applications. In this solution login could be handled by a User class
    (probably abstract), with subclasses for Student and Admin. Data for all
    types of users are stored in a single database table with a qualifying
    column (usually a type column) which designates the subclass of the User
    instance. Find more by searching for Single-table Inheritance, or STI.

  2. Polymorphic association
    This can be used to provide additional flexibility beyond that provided
    by STI. Google this for more information.

  3. Access Control Lists (ACL)
    This is the “industrial strength” solution. It is extremely flexible,
    also making it complex relative to 1 & 2 above.

Clinton Judy wrote:

I understand now. On my first attempt, I would try keeping Students and
Admins in separate tables. Then when someone tries to login, attempt to
match them to the Students table. If there are no matches, attempt to
match
them in the Admins table.

This is a very wet solution, but it would allow you to match many admins
with many schools, but only keep one school per student. Maybe someone
can
come up with a more dry solution that doesn’t make this harder to
maintain.

6

I understand now. On my first attempt, I would try keeping Students and
Admins in separate tables. Then when someone tries to login, attempt to
match them to the Students table. If there are no matches, attempt to
match
them in the Admins table.

This is a very wet solution, but it would allow you to match many admins
with many schools, but only keep one school per student. Maybe someone
can
come up with a more dry solution that doesn’t make this harder to
maintain.

7

Here is an article that covers some plugins/tool for Rails to help with
authentication and authorization. Maybe this will be helpful:

http://www.vaporbase.com/postings/Authorization_in_Rails

Robert W. wrote:

This is a very common scenario that comes up all the time. The problem
is that there isn’t a “silver bullet” solution for this. Different
applications often end up with different needs.