Ruby private inheritance

ruby_private_inheritance.rb

class Parent
  attr_accessor :a, :b
  def initialize(a)
    @a = a
  end
  private
  def set_b
    @b = 'b'
  end
end

class Child < Parent
  attr_accessor :c
  def initialize(c)
    @c = c
  end
  def set_c
    set_b
  end
end

c = Child.new('x')
# => #<Child:0x007f9989919680 @c="x">
c.a
# => nil
c.b
# => nil
c.c
# => "x"

c.set_c
# => "b"
c.a
# => nil
c.b
# => "b"
c.c
# => "x"