Model help with school app

rubyonrails-talk
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

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.

5

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

6

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:

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 Walker wrote: <snip>

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.

</snip>