iterator.rb

# Iterator helps you to iterate through a complex object using
# an iterator method

class Parent
  attr_reader :first_name

  def initialize(first_name, gender)
    @first_name = first_name
    @gender = gender
  end
end

class Child < Parent
end

class Family
  def initialize(surname)
    @surname = surname
    @children = []
  end

  def add_father(first_name)
    @father = Parent.new first_name, "M"
  end

  def add_mother(first_name)
    @mother = Parent.new first_name, "F"
  end

  def add_child(first_name, gender)
    @children << Child.new(first_name, gender)
  end

  def each_member
    [@father, @mother, @children].flatten.each do |member|
      yield member
    end
  end
end

# Usage
family = Family.new "Jackson"
family.add_father("Robert")
family.add_mother("Susan")
family.add_child("Lucas", "M")
family.add_child("James", "M")
family.add_child("Rose", "F")
family.each_member{ |member| puts member.first_name }
# => Robert
#    Susan
#    Lucas
#    James
#    Rose