Rails Model Relationships, user roles

Question

I asked a similar question a couple of days ago, but I realized that I didn't ask it quite right.
In a Rails app with Manager and Employee models, let's say that all managers are employees, but not all employees are managers. I needed a solution for a user to be able to act as a manager and employee, both having different attributes and methods.

I was told to use Single Table Inheritance, which is very useful, but that gave the user the properties of both at the same time. What I would like is for the user (not every user) to be able to act as a manager and employee, but not both at the same time.
So, some users can either be a manager or employee, but not both. Some users can only be an employee.

Any ideas on what relationship I should use for this?

Answer 1

You could use STI like so:

structure

create_table :users do |t|
  t.string :name
  t.string :type # index this
end

source

class User < ActiveRecord::Base
  # attributes -- name, type

  def to_s
    "#{name} (Generic User)"
  end
end

class Manager < User
  def to_s
    "#{name} (Manager)"
  end
end

class Employee < User
  def to_s
    "#{name} (Employee)"
  end
end

examples

puts User.new(name: "Mr User")
# => "Mr User (Generic User)"

puts Manager.new(name: "Mr Manager")
# => "Mr Manager (Manager)"

puts Employee.new(name: "Mr Employee")
# => "Mr Employee (Employee)"