devise.rb

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

class Device < ActiveRecord::Base
  belongs_to :user, touch: true
  before_create :generate_access_token
  validates :device_type, :name, :os, :user_id, presence: true

  private
  def generate_access_token
    self.token = SecureRandom.hex
  end
end

user.rb

# == Schema Information
#
# Table name: users
#
#  id                              :integer          not null, primary key
#  email                           :string(255)      not null
#  crypted_password                :string(255)      not null
#  salt                            :string(255)      not null
#  created_at                      :datetime
#  updated_at                      :datetime
#  admin                           :boolean          default(FALSE)
#  stripe_id                       :string(255)
#  last4                           :string(255)
#  name                            :string(255)
#

class User < ActiveRecord::Base

  validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i

  validates :email, :name, :password, :device_limit, :event_limit, :discount, presence: true
  validates :password, length: { minimum: 8 }
  validates :device_limit, numericality: { only_integer: true, :greater_than_or_equal_to => 0, :message => ' count is invalid' }
  validates :event_limit,  numericality: { only_integer: true, :greater_than_or_equal_to => 0, :message => ' count is invalid' }
  validates :discount,     numericality: { only_integer: true, :greater_than_or_equal_to => 0, :less_than_or_equal_to => 100, :message => ' is invalid' }

  has_many :devices, dependent: :destroy

  def update_card(token)
    if stripe_id.parent?
      customer = Stripe::Customer.retrieve(stripe_id)
    else
      customer = Stripe::Customer.create(email: email, description: "ID " + id.to_s)
      self.stripe_id = customer.id
      self.save      
    end
    card = customer.cards.create({ card: token }) # customer.source.create for new Stripe API
    customer.default_card = card.id # default_source for new Stripe API
    customer.save
    self.last4 = card[:last4]
    self.save
  end

  def add_new_device(device_attrs)
    raise Exceptions::DeviceLimitReached.new("device_limit_reached") if self.devices.count >= self.device_limit
    self.devices.create(device_attrs)
  end

end