Sieve of Eratosthenes

sieve.rb

class Sieve
  def initialize(limit)
    @number_list = (2..limit).to_a
  end

  def primes
    prime_numbers = []
    until @number_list.empty?
      prime_numbers << @number_list.first
      @number_list -= multiples_of @number_list.first
    end
    prime_numbers
  end

  private

  def multiples_of(first_number_in_list)
    @number_list.select { |number| number % first_number_in_list == 0 }
  end
end