demeter_delegation_1.rb

# Better: delegate credit_balance so MovieTheater only accesses Moviegoer
class Moviegoer
  def credit_balance
    self.wallet.credit_balance  # delegation
  end
end
class MovieTheater
  def collect_money(moviegoer,amount)
    if moviegoer.credit_balance >= amount
      moviegoer.credit_balance -= due_amount
      @collected_amount += due_amount
    else
      raise InsufficientFundsError
    end
  end
end