fizzbuzz.rb

class JoinFormatter
  def initialize(separator = '', default = '')
    @default = default
  end
  
  def format(elements)
    res_string = elements.join ''
    return @default if res_string == ''
    res_string
  end
end

class CheckRunner
  def initialize(checks, formatter, element)
    @checks = checks
    @formatter = formatter
    @element = element
  end
  
  def result
    @result ||= run
  end
  
  private
  
  def run
    @formatter.format(check_results)
  end
    
  def check_results
    @checks.map { |c| c.call(@element) }
  end
end

def fizz_buzz(number)
  fizz = ->(x){ 'fizz' if x % 3 == 0 }
  buzz = ->(x){ 'buzz' if x % 5 == 0 }
  CheckRunner.new([fizz, buzz], JoinFormatter.new('', number), number).result
end

def fizz_buzz_list(list)
  list_checker = ->(x) { x.map { |e| fizz_buzz(e) } }
  CheckRunner.new([list_checker], JoinFormatter.new('\n', 'no elements'), list).result 
end