Using attr_reader with ||= and getting interesting results

demo.rb

# ruby 2.5.0p0 (2017-12-25 revision 61468)
class Demo
  attr_reader :first_name

  def initialize(first_name)
    @first_name = first_name
  end

  def hi(myname = nil)
    puts "Hello, #{first_name}"
    first_name ||= myname
    puts "Hello, #{first_name}"
  end

  def test(myname = nil)
    puts "Hello, #{first_name}"
    first_name = first_name || myname
    puts "Hello, #{first_name}"
  end

  def hello(myname = nil)
    puts "Hello, #{first_name}"
    first_name = first_name ? first_name : myname
    puts "Hello, #{first_name}"
  end
end

# demo = Demo.new('John')
# demo.first_name #=> 'John'

# demo.hi('Bill') 
#=> Hello, John 
#=> Hello, Bill

# demo.test('Bill') 
#=> Hello, John 
#=> Hello, Bill

# demo.hello('Bill') 
#=> Hello, John 
#=> Hello, Bill