hello.rb

# frozen_string_literal: true

class Hello
  attr_reader :foo, :bar

  def initialize
    @foo = Foo.new(self)
    @bar = Bar.new(self)

    @foo.hello
    @bar.hello
  end
end

class Foo
  def initialize(hello)
    @hello = hello
  end

  def hello
    p @hello
  end
end

class Bar
  def initialize(hello)
    @hello = hello
  end

  def hello
    p @hello
  end
end

Hello.new