Concerning Ruby `protected` access modified

concerning_ruby_protected_access_modifier.rb

#!/usr/bin/env ruby 

class A

  def foo(other)
    puts "self: #{ bar }"
    puts "other: #{ other.bar }"
  end

  protected

  def bar
    "a"
  end

end

class B < A

  protected

  def bar
    "b"
  end

end

class C < A

  def bar
    "c"
  end

end

a = A.new
b = B.new
c = C.new

a.foo c
b.foo a
b.foo c
c.foo a

a.foo b # => raises 7:in `foo': protected method `bar' called for #<B:0x00000002486730> (NoMethodError)
c.foo b # => raises 7:in `foo': protected method `bar' called for #<B:0x00000001ffa770> (NoMethodError)

current_workaround.rb

#!/usr/bin/env ruby 

class A

  def foo(other)
    puts "self: #{ call_bar }"
    puts "other: #{ other.call_bar }"
  end

  protected

  def call_bar
    bar
  end

  def bar
    "a"
  end

end

class B < A

  protected

  def bar
    "b"
  end

end

class C < A

  def bar
    "c"
  end

end

a = A.new
b = B.new
c = C.new

a.foo c
b.foo a
b.foo c
c.foo a

a.foo b
c.foo b