ruby_ri20min.rb

class Greeter
  def initialize(*names)
    names << "World" if names.empty?
    @names = names
  end

  def say_hi
    @names.each do |name|
      puts "Hello #{name}!"
    end
  end

  def say_bye
    puts "Goodbye #{@names.join(", ")}. Come back soon!"
  end
end

Greeter.new.say_hi  
# Hello World!
Greeter.new.say_bye
# Goodbye World. Come back soon!

Greeter.new("Ross").say_hi  
# Hello Ross!
Greeter.new("Ross").say_bye
# Goodbye Ross. Come back soon!

Greeter.new("Ross", "Carl", "Megan").say_hi  
# Hello Ross!
# Hello Carl!
# Hello Megan!
Greeter.new("Ross", "Carl", "Megan").say_bye  
# Goodbye Ross, Carl, Megan. Come back soon!