assistant_trainer.rb

class AssistantTrainer < User
	belongs_to :trainer
end

console.txt

2.1.2 :035 > trainer
 => #<Trainer id: 3, email: "at2@at.com", encrypted_password: "$2a$10$ASt34cSOixmCw0JWe8BRQu8BhQSmK6WaAeqtzuDKDB....", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 2, current_sign_in_at: "2015-06-22 09:39:35", last_sign_in_at: "2015-06-19 06:57:11", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", created_at: "2015-06-19 06:57:11", updated_at: "2015-06-22 09:39:35", name: "at2", role: 0, type: "Trainer", trainer_id: nil> 
 
2.1.2 :036 > at
 => #<AssistantTrainer id: 1, email: "trainer@trainer.com", encrypted_password: "$2a$10$s29lmJAZOMFLXUWbcDQDWeYBf/dyihdUVkRmHEr4kMx...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 2, current_sign_in_at: "2015-06-19 06:57:40", last_sign_in_at: "2015-06-19 06:55:54", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", created_at: "2015-06-19 06:55:53", updated_at: "2015-06-22 08:58:14", name: "Trainer", role: 0, type: "AssistantTrainer", trainer_id: 3> 
 
2.1.2 :037 > new_at
 => #<User id: 4, email: "newat@sfl.co.za", encrypted_password: "$2a$10$7.xuBvnvEgkFEyFLEpBDmuxOWyPV43aCMNAuZvGzIRX...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 1, current_sign_in_at: "2015-06-29 09:18:04", last_sign_in_at: "2015-06-29 09:18:04", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", created_at: "2015-06-29 09:18:03", updated_at: "2015-06-29 09:32:31", name: nil, role: 0, type: "AssistantTrainer", trainer_id: 3> 
 
2.1.2 :038 > trainer.assistant_trainers
 => #<ActiveRecord::Associations::CollectionProxy [#<AssistantTrainer id: 1, email: "trainer@trainer.com", encrypted_password: "$2a$10$s29lmJAZOMFLXUWbcDQDWeYBf/dyihdUVkRmHEr4kMx...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 2, current_sign_in_at: "2015-06-19 06:57:40", last_sign_in_at: "2015-06-19 06:55:54", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", created_at: "2015-06-19 06:55:53", updated_at: "2015-06-22 08:58:14", name: "Trainer", role: 0, type: "AssistantTrainer", trainer_id: 3>, #<AssistantTrainer id: 4, email: "newat@sfl.co.za", encrypted_password: "$2a$10$7.xuBvnvEgkFEyFLEpBDmuxOWyPV43aCMNAuZvGzIRX...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 1, current_sign_in_at: "2015-06-29 09:18:04", last_sign_in_at: "2015-06-29 09:18:04", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", created_at: "2015-06-29 09:18:03", updated_at: "2015-06-29 09:32:31", name: nil, role: 0, type: "AssistantTrainer", trainer_id: 3>]> 
 
2.1.2 :039 > new_at.groups
  Group Load (4.2ms)  SELECT "groups".* FROM "groups"  WHERE "groups"."user_id" = $1  [["user_id", 4]]
  Group Load (4.2ms)  SELECT "groups".* FROM "groups"  WHERE "groups"."user_id" = $1  [["user_id", 4]]
 => #<ActiveRecord::Associations::CollectionProxy []> 
 
2.1.2 :040 > at.groups
 => #<ActiveRecord::Associations::CollectionProxy [#<Group id: 3, group_name: "assistant trainer group", area: nil, user_id: 1, avatar: nil, created_at: "2015-06-29 09:05:51", updated_at: "2015-06-29 09:05:51", group_picture_file_name: nil, group_picture_content_type: nil, group_picture_file_size: nil, group_picture_updated_at: nil>]> 
 
2.1.2 :042 > trainer.assistant_trainers.each do |t|
2.1.2 :043 >     t.groups
2.1.2 :044?>   end
 => [#<AssistantTrainer id: 1, email: "trainer@trainer.com", encrypted_password: "$2a$10$s29lmJAZOMFLXUWbcDQDWeYBf/dyihdUVkRmHEr4kMx...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 2, current_sign_in_at: "2015-06-19 06:57:40", last_sign_in_at: "2015-06-19 06:55:54", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", created_at: "2015-06-19 06:55:53", updated_at: "2015-06-22 08:58:14", name: "Trainer", role: 0, type: "AssistantTrainer", trainer_id: 3>, #<AssistantTrainer id: 4, email: "newat@sfl.co.za", encrypted_password: "$2a$10$7.xuBvnvEgkFEyFLEpBDmuxOWyPV43aCMNAuZvGzIRX...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 1, current_sign_in_at: "2015-06-29 09:18:04", last_sign_in_at: "2015-06-29 09:18:04", current_sign_in_ip: "127.0.0.1", last_sign_in_ip: "127.0.0.1", created_at: "2015-06-29 09:18:03", updated_at: "2015-06-29 09:32:31", name: nil, role: 0, type: "AssistantTrainer", trainer_id: 3>] 

trainer.rb

class Trainer < User
	has_many :assistant_trainers
end

user.rb

class User < ActiveRecord::Base
  enum role: [:user, :vip, :admin]
  after_initialize :set_default_role, :if => :new_record?
  #has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "100x100>" }, :default_url => "/images/:style/missing.png"
  #validates_attachment_content_type :avatar, :content_type => /\Aimage\/.*\Z/
  has_many :groups
  belongs_to :phone_rental
  has_many :gardeners, through: :groups

  def set_default_role
    self.role ||= :user
  end

  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
end