Trying to get started with ruby hello_world.

hello_world.rb

class HelloWorld

  def hello()
    'Hello, World!'
  end

end

irb.out

$ irb
2.3.0 :001 > require_relative 'hello_world'
 => true
2.3.0 :002 > HelloWorld.instance_methods(false)
 => [:hello]
2.3.0 :003 > HelloWorld.hello
NoMethodError: undefined method `hello' for HelloWorld:Class
        from (irb):3
        from /home/dawiest/.rvm/rubies/ruby-2.3.0/bin/irb:11:in `<main>'
2.3.0 :004 > hw = HelloWorld.new
 => #<HelloWorld:0x000000028ee750>
2.3.0 :005 > hw.hello
 => "Hello, World!"