Question

I’ve been struggling with something that’s probably very obvious:

When I try and assign courses to users, I don’t think it’s allowing for a course to be in the collection of more than one user.

I have a method which iterates through every user and assigns a subsection of every course to that user. Only the last few users have courses assigned to them. I think this is because the relationship between the two is stored as a field in the courses table, so a course can only belong to one user. I want courses to belong to many users.

Thinking about it, I’m assuming this is because I need another kind of relationship than has_many? Like HABTM?

I think I’m confused about how AR associations work…

user.rb

class User < ActiveRecord::Base
  has_many :courses
  has_many :bookmarks, :class_name => 'Course'

  attr_accessible :email, :password, :courses, :bookmarks

  validates_presence_of :password, :on => :create
  validates_presence_of :email, :on => :create
  validates :password, :length => { :in => 6..20 }
  validates_format_of :email, :with => /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i
  validates_uniqueness_of :email
end

# == Schema Information
#
# Table name: users
#
#  id              :integer         not null, primary key
#  email           :string(255)
#  password_digest :string(255)
#  course_id       :integer
#  bookmark_id     :integer
#  created_at      :datetime        not null
#  updated_at      :datetime        not null
#

course.rb

class Course < ActiveRecord::Base
  attr_accessible :name
end

# == Schema Information
#
# Table name: courses
#
#  id          :integer         not null, primary key
#  name        :string(255)
#  created_at  :datetime        not null
#  updated_at  :datetime        not null
#  user_id     :integer
#

Answer 1

You should go with HABTM, also you can delete user_id column from courses and course_id from users.

class User < ActiveRecord::Base
  has_many :course_users
  has_many :course, :through => :course_users
end

class Course < ActiveRecord::Base
  has_many :course_users
  has_many :users, :through => :course_users
end

class CourseUser < ActiveRecord::Base
  belongs_to :user
  belongs_to :course
# == Schema Information
#
# Table name: course_users
#
#  id          :integer         not null, primary key
#  created_at  :datetime        not null
#  updated_at  :datetime        not null
#  user_id     :integer
#  course_id     :integer
#
end