app/models/user.rb
class User < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable, :validatable
#:recoverable, :rememberable, :trackable,
has_many :collections, dependent: :destroy
has_many :monuments, through: :collections
end