has_many多态关联的Rails可能出现的问题

Question

In my application, I have the following models:

User

Psychologist has_many classrooms

Teacher has_many classrooms

Parent has_many children

Director belongs_to school

Coordinator belongs_to school

My user model looks like the following:

class User < ActiveRecord
   has_many :roles

   def has_role? role_name
     self.roles.where(role_type: role_name).any?
   end
end

The Role model is polymorphic:

class Role < ApplicationRecord
  belongs_to :user
  belongs_to :roleable, polymorphic: true
end

And the other models are rollable.

My question is the following, it seems that this is not correct, because some models like: Director, Psychologists, Teachers, Coordinator and Parent. They only have relationships and their database tables do not have any other column except created_at , updated_at .

Is it okay to only create these models with relationships and have their tables without data?

Answer 1

Maybe you intend to use single table inheritance and not polymorphic relationships . If a Psychologist is a User , it should be the case.

Then you need to add a type column of type VARCHAR to the users table, and set up your models like:

class User < ApplicationRecord
  has_many :roles

  def has_role? role_name
    self.roles.where(role_type: role_name).any?
  end
end

class Psychologist < User
  # no need to set up roles
end

class Teacher < User
  # no need to set up roles
end

class Role < ApplicationRecord
  belongs_to :user
  # no polymorphic
end

The type column will be populated with the name of the actual class, like "Teacher" etc.

As an instance of Teacher is also an instance of User , it will have teacher.has_role?('foo') and teacher.roles , and you will be able to create a role like Role.create(user: teacher, name: 'bar') .