uninitialized user?

ability.rb

class Ability
  include CanCan::Ability

  def initialize(user, options = {})
    user ? user_rules : guest_rules
  end

  def user_rules
    user.roles.each { |role| exec_role_rules(role) if user.roles.include? role }
    default_roles
  end

  def exec_role_rules(role)
    meth = :"#{user.role}_rules"
    send(meth) if respond_to? meth
  end

  def admin_rules
    can :manage, :all
  end

  def boss_rules
    can :manage, :all
  end

  def exporter_rules
  end

  def member_rules

  end

  def guest_rules
    can :read, Pages
    can :create, Organization
    can :create, User
  end
end

error

undefined local variable or method `user' for #<Ability:0x007fd291ff1228>

Rails.root: /Users/derek/glide_projects/mdm
Application Trace | Framework Trace | Full Trace

app/models/ability.rb:10:in `user_rules'
app/models/ability.rb:6:in `initialize'