Collect primes using Sieve of Eratosthenes

prime_collector.rb

module PrimalityChecker
  module EratosthenesSieve
    def self.prime?(n)
      # Start at 7, because the obvious ones are crossed out
      !(7..Math.sqrt(n)).any? {|p| n % p == 0 }
    end
  end
end

class PrimeCollector
  include Enumerable

  def prime?(n, primality_checker = PrimalityChecker::EratostheneseSieve)
    return true if [1,2,3,5].include?(n)
    return false if [3,5].any?{|p| n % p == 0}
    return false if n.even? # This line is useless, because of .step(@limit, 2) in #each
    primality_checker.prime?(n)
  end

  def initialize(limit = 1000)
    @limit = limit
  end

  def each(&block)
    [2, *3.step(@limit, 2)].select(&method(:prime?)).each(&block)
  end
end

prime_collector = PrimeCollector.new(1000)
primes = prime_collector.map{|p| p};0