ActiveRecord::HasManyThroughAssociationNotFoundError - Ruby on Rails

Question

I am working on a STMS. While am trying to model things out and try to add a new record for students table via:

stud = Student.create(:student_id => 1, :first_name => 'Jos', :last_name => 'Norton', :email => 'ss.norton@gmail.com', :birthday => '12/05/1995', :subjects => 'English', :username => 'samnorton05', :password => 'Grace02112')

I got an error:

ActiveRecord::HasManyThroughAssociationNotFoundError: Could not find the association :enrolled_subjects in model Student 

Here's the models I am using:

class Student < ApplicationRecord

  has_many :subjects, through: :enrolled_subjects
  has_many :teachers, through: :enrolled_subjects

  def teacher_names
    self.teachers.map(&:name).join(", ")
  end

  has_many :admin_users
  has_secure_password
  self.primary_key = :student_id


  scope :newest_first, lambda { order("created_at ASC") }
  scope :oldest_first, lambda { order("created_at DESC") }
  # scope :search, lambda { |query| where(["name LIKE ?", "%#{query}%"])}

end

class Teacher < ApplicationRecord

  has_many :subjects, through: :enrolled_subjects
  has_many :students, through: :enrolled_subjects
  has_many :admin_users
  has_secure_password

  scope :newest_first, lambda { order("created_at ASC") }
  scope :oldest_first, lambda { order("created_at DESC") }
  # scope :search, lambda { |query| where(["name LIKE ?", "%#{query}%"])}
end

class Subject < ApplicationRecord

  has_many :students, through: :enrolled_subjects
  has_many :teachers, through: :enrolled_subjects
  has_many :admin_users

  # scope :search, lambda { |query| where(["name LIKE ?", "%#{query}%"])}

end

class EnrolledSubject < ApplicationRecord
  belongs_to :student
  belongs_to :subject
  belongs_to :teacher
end

class AdminUser < ApplicationRecord

  has_secure_password

  scope :newest_first, lambda { order("created_at ASC") }
  scope :oldest_first, lambda { order("created_at DESC") }
  # scope :search, lambda { |query| where(["name LIKE ?", "%#{query}%"])}
end

Basically I have 5 tables namely: Students, teachers, subjects, admin users and enrolled subjects. Any idea what am I doing wrong? Sorry I am a newbie here.

EDIT HERE ARE MY MIGRATION:

 create_table :students, :id => false do |t|
    t.integer "student_id", :auto_increment => true, :primary_key => true
    t.string "first_name", :limit => 25
    t.string "last_name", :limit => 50
    t.string "email", :default => ' ', :null => false
    t.string "birthday"
    t.string "subjects"
    t.string "username", :limit => 25
    t.string "password_digest"
    t.timestamps
  end

  create_table :teachers, :id => false do |t|
      t.integer "teacher_id", :auto_increment => true, :primary_key => true
      t.string "first_name"
      t.string "last_name"
      t.string "email", :default => ' ', :null => false
      t.string "birthday"
      t.string "subjects"
      t.string "username", :limit => 25
      t.string "password_digest"
      t.timestamps
    end

Answer 1

You should add the enrolled_subjects as well, like:

class Student < ApplicationRecord
  # first you add the association to enrolled_subjects
  has_many :enrolled_subjects
  # then you add the associations you has through it
  has_many :subjects, through: :enrolled_subjects
  has_many :teachers, through: :enrolled_subjects

end