public vs private vs protected in Ruby

public_private_protected.rb

class A
  def test
    self.call_private("A") rescue p 'cannot call self.call_private("A")'
    call_private("A")

    call_protected("A")
    self.call_protected("A")
  end

  protected

  def call_protected(from)
    p "protected call from #{from}"
  end

  private
  def call_private(from)
    p "private call from #{from}"
  end
end

class AB < A
end

class AC < A
  def test
    self.call_private("AC") rescue p 'cannot call self.call_private("AC")'
    call_private("AC")

    call_protected("AC")
    self.call_protected("AC")

    ab = AB.new
    ab.call_protected("AC")
    ab.call_private("AC") rescue  p 'cannot call ab.call_private("AC")'
  end
end

class B
  def test
    a = A.new
    a.test
    a.call_protected("B") rescue 'cannot call a.call_protected("B")'
    a.call_private("B") rescue 'cannot call a.call_private("B")'

    ac = AC.new
    ac.test
    ac.call_protected("AC") rescue 'cannot call ac.call_protected("AC")'
    ac.call_private("AC") rescue 'cannot call ac.call_private("AC")'
  end
end

B.new.test